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Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
'\" te
.\" Copyright (c) 2013 by Turbo Fredriksson <turbo@bayour.com>. All rights reserved.
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 04:27:01 +03:00
.\" Copyright (c) 2017 Datto Inc.
Add tunables for channel programs This patch adds tunables for modifying the maximum memory limit and maximum instruction limit that can be specified when running a channel program. Reviewed-by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov Reviewed-by: Sara Hartse <sara.hartse@delphix.com> Signed-off-by: John Gallagher <john.gallagher@delphix.com> External-issue: LX-1085 Closes #7618
2018-06-16 01:10:42 +03:00
.\" Copyright (c) 2018 by Delphix. All rights reserved.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.\" The contents of this file are subject to the terms of the Common Development
.\" and Distribution License (the "License"). You may not use this file except
.\" in compliance with the License. You can obtain a copy of the license at
.\" usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing.
.\"
.\" See the License for the specific language governing permissions and
.\" limitations under the License. When distributing Covered Code, include this
.\" CDDL HEADER in each file and include the License file at
.\" usr/src/OPENSOLARIS.LICENSE. If applicable, add the following below this
.\" CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your
.\" own identifying information:
.\" Portions Copyright [yyyy] [name of copyright owner]
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 04:27:01 +03:00
.TH ZFS-MODULE-PARAMETERS 5 "Oct 28, 2017"
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.SH NAME
zfs\-module\-parameters \- ZFS module parameters
.SH DESCRIPTION
.sp
.LP
Description of the different parameters to the ZFS module.
.SS "Module parameters"
.sp
.LP
OpenZFS 9188 - increase size of dbuf cache to reduce indirect block decompression With compressed ARC (bug 6950) we use up to 25% of our CPU to decompress indirect blocks, under a workload of random cached reads. To reduce this decompression cost, we would like to increase the size of the dbuf cache so that more indirect blocks can be stored uncompressed. If we are caching entire large files of recordsize=8K, the indirect blocks use 1/64th as much memory as the data blocks (assuming they have the same compression ratio). We suggest making the dbuf cache be 1/32nd of all memory, so that in this scenario we should be able to keep all the indirect blocks decompressed in the dbuf cache. (We want it to be more than the 1/64th that the indirect blocks would use because we need to cache other stuff in the dbuf cache as well.) In real world workloads, this won't help as dramatically as the example above, but we think it's still worth it because the risk of decreasing performance is low. The potential negative performance impact is that we will be slightly reducing the size of the ARC (by ~3%). Porting Notes: * Added modules options to zfs-module-parameters.5 man page. * Preserved scaling based on target ARC size rather than max ARC size. Authored by: George Wilson <george.wilson@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Prashanth Sreenivasa <pks@delphix.com> Reviewed by: Paul Dagnelie <pcd@delphix.com> Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/9188 OpenZFS-commit: https://github.com/openzfs/openzfs/pull/564 Upstream bug: DLPX-46942 Closes #7273
2018-03-13 20:52:48 +03:00
.sp
.ne 2
.na
\fBdbuf_cache_max_bytes\fR (ulong)
.ad
.RS 12n
Maximum size in bytes of the dbuf cache. When \fB0\fR this value will default
to \fB1/2^dbuf_cache_shift\fR (1/32) of the target ARC size, otherwise the
provided value in bytes will be used. The behavior of the dbuf cache and its
associated settings can be observed via the \fB/proc/spl/kstat/zfs/dbufstats\fR
kstat.
.sp
Default value: \fB0\fR.
.RE
OpenZFS 9337 - zfs get all is slow due to uncached metadata This project's goal is to make read-heavy channel programs and zfs(1m) administrative commands faster by caching all the metadata that they will need in the dbuf layer. This will prevent the data from being evicted, so that any future call to i.e. zfs get all won't have to go to disk (very much). There are two parts: The dbuf_metadata_cache. We identify what to put into the cache based on the object type of each dbuf. Caching objset properties os {version,normalization,utf8only,casesensitivity} in the objset_t. The reason these needed to be cached is that although they are queried frequently, they aren't stored in a dbuf type which we can easily recognize and cache in the dbuf layer; instead, we have to explicitly store them. There's already existing infrastructure for maintaining cached properties in the objset setup code, so I simply used that. Performance Testing: - Disabled kmem_flags - Tuned dbuf_cache_max_bytes very low (128K) - Tuned zfs_arc_max very low (64M) Created test pool with 400 filesystems, and 100 snapshots per filesystem. Later on in testing, added 600 more filesystems (with no snapshots) to make sure scaling didn't look different between snapshots and filesystems. Results: | Test | Time (trunk / diff) | I/Os (trunk / diff) | +------------------------+---------------------+---------------------+ | zpool import | 0:05 / 0:06 | 12.9k / 12.9k | | zfs get all (uncached) | 1:36 / 0:53 | 16.7k / 5.7k | | zfs get all (cached) | 1:36 / 0:51 | 16.0k / 6.0k | Authored by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Thomas Caputi <tcaputi@datto.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Richard Lowe <richlowe@richlowe.net> Ported-by: Alek Pinchuk <apinchuk@datto.com> Signed-off-by: Alek Pinchuk <apinchuk@datto.com> OpenZFS-issue: https://illumos.org/issues/9337 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/7dec52f Closes #7668
2018-07-10 20:49:50 +03:00
.sp
.ne 2
.na
\fBdbuf_metadata_cache_max_bytes\fR (ulong)
.ad
.RS 12n
Maximum size in bytes of the metadata dbuf cache. When \fB0\fR this value will
default to \fB1/2^dbuf_cache_shift\fR (1/16) of the target ARC size, otherwise
the provided value in bytes will be used. The behavior of the metadata dbuf
cache and its associated settings can be observed via the
\fB/proc/spl/kstat/zfs/dbufstats\fR kstat.
.sp
Default value: \fB0\fR.
.RE
OpenZFS 9188 - increase size of dbuf cache to reduce indirect block decompression With compressed ARC (bug 6950) we use up to 25% of our CPU to decompress indirect blocks, under a workload of random cached reads. To reduce this decompression cost, we would like to increase the size of the dbuf cache so that more indirect blocks can be stored uncompressed. If we are caching entire large files of recordsize=8K, the indirect blocks use 1/64th as much memory as the data blocks (assuming they have the same compression ratio). We suggest making the dbuf cache be 1/32nd of all memory, so that in this scenario we should be able to keep all the indirect blocks decompressed in the dbuf cache. (We want it to be more than the 1/64th that the indirect blocks would use because we need to cache other stuff in the dbuf cache as well.) In real world workloads, this won't help as dramatically as the example above, but we think it's still worth it because the risk of decreasing performance is low. The potential negative performance impact is that we will be slightly reducing the size of the ARC (by ~3%). Porting Notes: * Added modules options to zfs-module-parameters.5 man page. * Preserved scaling based on target ARC size rather than max ARC size. Authored by: George Wilson <george.wilson@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Prashanth Sreenivasa <pks@delphix.com> Reviewed by: Paul Dagnelie <pcd@delphix.com> Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/9188 OpenZFS-commit: https://github.com/openzfs/openzfs/pull/564 Upstream bug: DLPX-46942 Closes #7273
2018-03-13 20:52:48 +03:00
.sp
.ne 2
.na
\fBdbuf_cache_hiwater_pct\fR (uint)
.ad
.RS 12n
The percentage over \fBdbuf_cache_max_bytes\fR when dbufs must be evicted
directly.
.sp
Default value: \fB10\fR%.
.RE
.sp
.ne 2
.na
\fBdbuf_cache_lowater_pct\fR (uint)
.ad
.RS 12n
The percentage below \fBdbuf_cache_max_bytes\fR when the evict thread stops
evicting dbufs.
.sp
Default value: \fB10\fR%.
.RE
.sp
.ne 2
.na
\fBdbuf_cache_shift\fR (int)
.ad
.RS 12n
Set the size of the dbuf cache, \fBdbuf_cache_max_bytes\fR, to a log2 fraction
of the target arc size.
.sp
Default value: \fB5\fR.
.RE
OpenZFS 9337 - zfs get all is slow due to uncached metadata This project's goal is to make read-heavy channel programs and zfs(1m) administrative commands faster by caching all the metadata that they will need in the dbuf layer. This will prevent the data from being evicted, so that any future call to i.e. zfs get all won't have to go to disk (very much). There are two parts: The dbuf_metadata_cache. We identify what to put into the cache based on the object type of each dbuf. Caching objset properties os {version,normalization,utf8only,casesensitivity} in the objset_t. The reason these needed to be cached is that although they are queried frequently, they aren't stored in a dbuf type which we can easily recognize and cache in the dbuf layer; instead, we have to explicitly store them. There's already existing infrastructure for maintaining cached properties in the objset setup code, so I simply used that. Performance Testing: - Disabled kmem_flags - Tuned dbuf_cache_max_bytes very low (128K) - Tuned zfs_arc_max very low (64M) Created test pool with 400 filesystems, and 100 snapshots per filesystem. Later on in testing, added 600 more filesystems (with no snapshots) to make sure scaling didn't look different between snapshots and filesystems. Results: | Test | Time (trunk / diff) | I/Os (trunk / diff) | +------------------------+---------------------+---------------------+ | zpool import | 0:05 / 0:06 | 12.9k / 12.9k | | zfs get all (uncached) | 1:36 / 0:53 | 16.7k / 5.7k | | zfs get all (cached) | 1:36 / 0:51 | 16.0k / 6.0k | Authored by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Thomas Caputi <tcaputi@datto.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Richard Lowe <richlowe@richlowe.net> Ported-by: Alek Pinchuk <apinchuk@datto.com> Signed-off-by: Alek Pinchuk <apinchuk@datto.com> OpenZFS-issue: https://illumos.org/issues/9337 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/7dec52f Closes #7668
2018-07-10 20:49:50 +03:00
.sp
.ne 2
.na
\fBdbuf_metadata_cache_shift\fR (int)
.ad
.RS 12n
Set the size of the dbuf metadata cache, \fBdbuf_metadata_cache_max_bytes\fR,
to a log2 fraction of the target arc size.
.sp
Default value: \fB6\fR.
.RE
Add tunable to ignore hole_birth Adds a module option which disables the hole_birth optimization which has been responsible for several recent bugs, including issue #4050. Original-patch: https://gist.github.com/pcd1193182/2c0cd47211f3aee623958b4698836c48 Signed-off-by: Rich Ercolani <rincebrain@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4833
2016-07-08 23:51:50 +03:00
.sp
.ne 2
.na
\fBignore_hole_birth\fR (int)
.ad
.RS 12n
When set, the hole_birth optimization will not be used, and all holes will
always be sent on zfs send. Useful if you suspect your datasets are affected
by a bug in hole_birth.
.sp
Enable ignore_hole_birth module option by default Enable ignore_hole_birth by default until all known hole birth bugs have been resolved and relevant test cases added. Reviewed-by: Boris Protopopov <boris.protopopov@actifio.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #4809 Closes #5099
2016-09-17 00:05:30 +03:00
Use \fB1\fR for on (default) and \fB0\fR for off.
Add tunable to ignore hole_birth Adds a module option which disables the hole_birth optimization which has been responsible for several recent bugs, including issue #4050. Original-patch: https://gist.github.com/pcd1193182/2c0cd47211f3aee623958b4698836c48 Signed-off-by: Rich Ercolani <rincebrain@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4833
2016-07-08 23:51:50 +03:00
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
.ne 2
.na
\fBl2arc_feed_again\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Turbo L2ARC warm-up. When the L2ARC is cold the fill interval will be set as
fast as possible.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Use \fB1\fR for yes (default) and \fB0\fR to disable.
.RE
.sp
.ne 2
.na
\fBl2arc_feed_min_ms\fR (ulong)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Min feed interval in milliseconds. Requires \fBl2arc_feed_again=1\fR and only
applicable in related situations.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Default value: \fB200\fR.
.RE
.sp
.ne 2
.na
\fBl2arc_feed_secs\fR (ulong)
.ad
.RS 12n
Seconds between L2ARC writing
.sp
Default value: \fB1\fR.
.RE
.sp
.ne 2
.na
\fBl2arc_headroom\fR (ulong)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
How far through the ARC lists to search for L2ARC cacheable content, expressed
as a multiplier of \fBl2arc_write_max\fR
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Default value: \fB2\fR.
.RE
.sp
.ne 2
.na
\fBl2arc_headroom_boost\fR (ulong)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Scales \fBl2arc_headroom\fR by this percentage when L2ARC contents are being
successfully compressed before writing. A value of 100 disables this feature.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 22:51:11 +03:00
Default value: \fB200\fR%.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.RE
.sp
.ne 2
.na
\fBl2arc_noprefetch\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Do not write buffers to L2ARC if they were prefetched but not used by
applications
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Use \fB1\fR for yes (default) and \fB0\fR to disable.
.RE
.sp
.ne 2
.na
\fBl2arc_norw\fR (int)
.ad
.RS 12n
No reads during writes
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
.sp
.ne 2
.na
\fBl2arc_write_boost\fR (ulong)
.ad
.RS 12n
Fix typo in zfs-module-parameters man page Fix typo in zfs-module-parameters man page Reviewed-by: Richard Laager <rlaager@wiktel.com> Reviewed-by: Mike McQuaid <mike@mikemcquaid.com> Reviewed-by: Paul Dagnelie <pcd@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Gvozden Neskovic <neskovic@gmail.com> Reviewed-by: Neal Gompa <ngompa13@gmail.com> Reviewed-by: Jason Zaman <jason@perfinion.com> Reviewed-by: Ned Bass <bass6@llnl.gov> Reviewed-by: Jorgen Lundman <lundman@lundman.net> Reviewed-by: Prakash Surya <prakash.surya@delphix.com> Reviewed-by: Hajo Möller <dasjoe@gmail.com> Reviewed-by: Igor Kozhukhov <ikozhukhov@gmail.com> Reviewed-by: Richard Yao <ryao@gentoo.org> Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed-by: DHE <git@dehacked.net> Reviewed-by: Matthew Thode <prometheanfire@gentoo.org> Reviewed-by: Thomas Caputi <tcaputi@datto.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: kernelOfTruth <kerneloftruth@gmail.com> Reviewed-by: Kash Pande <kash@tripleback.net> Reviewed-by: ilovezfs <ilovezfs@icloud.com> Reviewed-by: @jwittlincohen Reviewed-by: Jack Draak <jackdraak@gmail.com> Reviewed-by: @ptx0 Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Reviewed-by: @Kokokokoka Reviewed-by: @JCount <JCount@hush.ai> Signed-off-by: bunder2015 <omfgbunder@gmail.com> Closes #6054
2017-04-24 20:56:44 +03:00
Cold L2ARC devices will have \fBl2arc_write_max\fR increased by this amount
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
while they remain cold.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Default value: \fB8,388,608\fR.
.RE
.sp
.ne 2
.na
\fBl2arc_write_max\fR (ulong)
.ad
.RS 12n
Max write bytes per interval
.sp
Default value: \fB8,388,608\fR.
.RE
Make metaslab_aliquot a module parameter. This seems generally useful. metaslab_aliquot is the ZFS allocation granularity, which is roughly equivalent to what is called the stripe size in traditional RAID arrays. It seems relevant to performance tuning. Signed-off-by: Etienne Dechamps <etienne@edechamps.fr> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2015-05-10 18:40:20 +03:00
.sp
.ne 2
.na
\fBmetaslab_aliquot\fR (ulong)
.ad
.RS 12n
Metaslab granularity, in bytes. This is roughly similar to what would be
referred to as the "stripe size" in traditional RAID arrays. In normal
operation, ZFS will try to write this amount of data to a top-level vdev
before moving on to the next one.
.sp
Default value: \fB524,288\fR.
.RE
Illumos 4976-4984 - metaslab improvements 4976 zfs should only avoid writing to a failing non-redundant top-level vdev 4978 ztest fails in get_metaslab_refcount() 4979 extend free space histogram to device and pool 4980 metaslabs should have a fragmentation metric 4981 remove fragmented ops vector from block allocator 4982 space_map object should proactively upgrade when feature is enabled 4983 need to collect metaslab information via mdb 4984 device selection should use fragmentation metric Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Adam Leventhal <adam.leventhal@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Approved by: Garrett D'Amore <garrett@damore.org> References: https://www.illumos.org/issues/4976 https://www.illumos.org/issues/4978 https://www.illumos.org/issues/4979 https://www.illumos.org/issues/4980 https://www.illumos.org/issues/4981 https://www.illumos.org/issues/4982 https://www.illumos.org/issues/4983 https://www.illumos.org/issues/4984 https://github.com/illumos/illumos-gate/commit/2e4c998 Notes: The "zdb -M" option has been re-tasked to display the new metaslab fragmentation metric and the new "zdb -I" option is used to control the maximum number of in-flight I/Os. The new fragmentation metric is derived from the space map histogram which has been rolled up to the vdev and pool level and is presented to the user via "zpool list". Add a number of module parameters related to the new metaslab weighting logic. Ported by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2595
2014-07-20 00:19:24 +04:00
.sp
.ne 2
.na
\fBmetaslab_bias_enabled\fR (int)
.ad
.RS 12n
Enable metaslab group biasing based on its vdev's over- or under-utilization
relative to the pool.
.sp
Use \fB1\fR for yes (default) and \fB0\fR for no.
.RE
OpenZFS 9280 - Assertion failure while running removal_with_ganging test with 4K devices Authored by: Matt Ahrens <Matt.Ahrens@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: John Kennedy <john.kennedy@delphix.com> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Approved by: Garrett D'Amore <garrett@damore.org> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/9280 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/243952c Closes #7445
2017-07-24 21:07:39 +03:00
.sp
.ne 2
.na
\fBmetaslab_force_ganging\fR (ulong)
.ad
.RS 12n
Make some blocks above a certain size be gang blocks. This option is used
by the test suite to facilitate testing.
.sp
Default value: \fB16,777,217\fR.
.RE
OpenZFS 7303 - dynamic metaslab selection This change introduces a new weighting algorithm to improve metaslab selection. The new weighting algorithm relies on the SPACEMAP_HISTOGRAM feature. As a result, the metaslab weight now encodes the type of weighting algorithm used (size-based vs segment-based). Porting Notes: The metaslab allocation tracing code is conditionally removed on linux (dependent on mdb debugger). Authored by: George Wilson <george.wilson@delphix.com> Reviewed by: Alex Reece <alex@delphix.com> Reviewed by: Chris Siden <christopher.siden@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Paul Dagnelie <paul.dagnelie@delphix.com> Reviewed by: Pavel Zakharov pavel.zakharov@delphix.com Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Don Brady <don.brady@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Ported-by: Don Brady <don.brady@intel.com> OpenZFS-issue: https://www.illumos.org/issues/7303 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/d5190931bd Closes #5404
2017-01-12 22:52:56 +03:00
.sp
.ne 2
.na
\fBzfs_metaslab_segment_weight_enabled\fR (int)
.ad
.RS 12n
Enable/disable segment-based metaslab selection.
.sp
Use \fB1\fR for yes (default) and \fB0\fR for no.
.RE
.sp
.ne 2
.na
\fBzfs_metaslab_switch_threshold\fR (int)
.ad
.RS 12n
When using segment-based metaslab selection, continue allocating
Typo in zfs-module-parameters(5) Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: DHE <git@dehacked.net> Closes #6061
2017-04-24 20:34:37 +03:00
from the active metaslab until \fBzfs_metaslab_switch_threshold\fR
OpenZFS 7303 - dynamic metaslab selection This change introduces a new weighting algorithm to improve metaslab selection. The new weighting algorithm relies on the SPACEMAP_HISTOGRAM feature. As a result, the metaslab weight now encodes the type of weighting algorithm used (size-based vs segment-based). Porting Notes: The metaslab allocation tracing code is conditionally removed on linux (dependent on mdb debugger). Authored by: George Wilson <george.wilson@delphix.com> Reviewed by: Alex Reece <alex@delphix.com> Reviewed by: Chris Siden <christopher.siden@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Paul Dagnelie <paul.dagnelie@delphix.com> Reviewed by: Pavel Zakharov pavel.zakharov@delphix.com Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Don Brady <don.brady@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Ported-by: Don Brady <don.brady@intel.com> OpenZFS-issue: https://www.illumos.org/issues/7303 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/d5190931bd Closes #5404
2017-01-12 22:52:56 +03:00
worth of buckets have been exhausted.
.sp
Default value: \fB2\fR.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
.ne 2
.na
Illumos #4101 finer-grained control of metaslab_debug Today the metaslab_debug logic performs two tasks: - load all metaslabs on import/open - don't unload metaslabs at the end of spa_sync This change provides knobs for each of these independently. References: https://illumos.org/issues/4101 https://github.com/illumos/illumos-gate/commit/0713e23 Notes: 1) This is a small piece of the metaslab improvement patch from Illumos. It was worth bringing over before the rest, since it's low risk and it can be useful on fragmented pools (e.g. Lustre MDTs). metaslab_debug_unload would give the performance benefit of the old metaslab_debug option without causing unwanted delay during pool import. Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2227
2014-04-01 04:22:55 +04:00
\fBmetaslab_debug_load\fR (int)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.ad
.RS 12n
Illumos #4101 finer-grained control of metaslab_debug Today the metaslab_debug logic performs two tasks: - load all metaslabs on import/open - don't unload metaslabs at the end of spa_sync This change provides knobs for each of these independently. References: https://illumos.org/issues/4101 https://github.com/illumos/illumos-gate/commit/0713e23 Notes: 1) This is a small piece of the metaslab improvement patch from Illumos. It was worth bringing over before the rest, since it's low risk and it can be useful on fragmented pools (e.g. Lustre MDTs). metaslab_debug_unload would give the performance benefit of the old metaslab_debug option without causing unwanted delay during pool import. Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2227
2014-04-01 04:22:55 +04:00
Load all metaslabs during pool import.
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
.sp
.ne 2
.na
\fBmetaslab_debug_unload\fR (int)
.ad
.RS 12n
Prevent metaslabs from being unloaded.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
Illumos 4976-4984 - metaslab improvements 4976 zfs should only avoid writing to a failing non-redundant top-level vdev 4978 ztest fails in get_metaslab_refcount() 4979 extend free space histogram to device and pool 4980 metaslabs should have a fragmentation metric 4981 remove fragmented ops vector from block allocator 4982 space_map object should proactively upgrade when feature is enabled 4983 need to collect metaslab information via mdb 4984 device selection should use fragmentation metric Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Adam Leventhal <adam.leventhal@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Approved by: Garrett D'Amore <garrett@damore.org> References: https://www.illumos.org/issues/4976 https://www.illumos.org/issues/4978 https://www.illumos.org/issues/4979 https://www.illumos.org/issues/4980 https://www.illumos.org/issues/4981 https://www.illumos.org/issues/4982 https://www.illumos.org/issues/4983 https://www.illumos.org/issues/4984 https://github.com/illumos/illumos-gate/commit/2e4c998 Notes: The "zdb -M" option has been re-tasked to display the new metaslab fragmentation metric and the new "zdb -I" option is used to control the maximum number of in-flight I/Os. The new fragmentation metric is derived from the space map histogram which has been rolled up to the vdev and pool level and is presented to the user via "zpool list". Add a number of module parameters related to the new metaslab weighting logic. Ported by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2595
2014-07-20 00:19:24 +04:00
.sp
.ne 2
.na
\fBmetaslab_fragmentation_factor_enabled\fR (int)
.ad
.RS 12n
Enable use of the fragmentation metric in computing metaslab weights.
.sp
Use \fB1\fR for yes (default) and \fB0\fR for no.
.RE
Illumos 5161 - add tunable for number of metaslabs per vdev 5161 add tunable for number of metaslabs per vdev Reviewed by: Alex Reece <alex.reece@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Paul Dagnelie <paul.dagnelie@delphix.com> Reviewed by: Saso Kiselkov <skiselkov.ml@gmail.com> Reviewed by: Richard Elling <richard.elling@gmail.com> Approved by: Richard Lowe <richlowe@richlowe.net> References: https://www.illumos.org/issues/5161 https://github.com/illumos/illumos-gate/commit/bf3e216 Ported by: Turbo Fredriksson <turbo@bayour.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2698
2014-09-13 18:13:00 +04:00
.sp
.ne 2
.na
OpenZFS 9166 - zfs storage pool checkpoint Details about the motivation of this feature and its usage can be found in this blogpost: https://sdimitro.github.io/post/zpool-checkpoint/ A lightning talk of this feature can be found here: https://www.youtube.com/watch?v=fPQA8K40jAM Implementation details can be found in big block comment of spa_checkpoint.c Side-changes that are relevant to this commit but not explained elsewhere: * renames members of "struct metaslab trees to be shorter without losing meaning * space_map_{alloc,truncate}() accept a block size as a parameter. The reason is that in the current state all space maps that we allocate through the DMU use a global tunable (space_map_blksz) which defauls to 4KB. This is ok for metaslab space maps in terms of bandwirdth since they are scattered all over the disk. But for other space maps this default is probably not what we want. Examples are device removal's vdev_obsolete_sm or vdev_chedkpoint_sm from this review. Both of these have a 1:1 relationship with each vdev and could benefit from a bigger block size. Porting notes: * The part of dsl_scan_sync() which handles async destroys has been moved into the new dsl_process_async_destroys() function. * Remove "VERIFY(!(flags & FWRITE))" in "kernel.c" so zhack can write to block device backed pools. * ZTS: * Fix get_txg() in zpool_sync_001_pos due to "checkpoint_txg". * Don't use large dd block sizes on /dev/urandom under Linux in checkpoint_capacity. * Adopt Delphix-OS's setting of 4 (spa_asize_inflation = SPA_DVAS_PER_BP + 1) for the checkpoint_capacity test to speed its attempts to fill the pool * Create the base and nested pools with sync=disabled to speed up the "setup" phase. * Clear labels in test pool between checkpoint tests to avoid duplicate pool issues. * The import_rewind_device_replaced test has been marked as "known to fail" for the reasons listed in its DISCLAIMER. * New module parameters: zfs_spa_discard_memory_limit, zfs_remove_max_bytes_pause (not documented - debugging only) vdev_max_ms_count (formerly metaslabs_per_vdev) vdev_min_ms_count Authored by: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: John Kennedy <john.kennedy@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Richard Lowe <richlowe@richlowe.net> Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Tim Chase <tim@chase2k.com> OpenZFS-issue: https://illumos.org/issues/9166 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/7159fdb8 Closes #7570
2016-12-17 01:11:29 +03:00
\fBvdev_max_ms_count\fR (int)
Illumos 5161 - add tunable for number of metaslabs per vdev 5161 add tunable for number of metaslabs per vdev Reviewed by: Alex Reece <alex.reece@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Paul Dagnelie <paul.dagnelie@delphix.com> Reviewed by: Saso Kiselkov <skiselkov.ml@gmail.com> Reviewed by: Richard Elling <richard.elling@gmail.com> Approved by: Richard Lowe <richlowe@richlowe.net> References: https://www.illumos.org/issues/5161 https://github.com/illumos/illumos-gate/commit/bf3e216 Ported by: Turbo Fredriksson <turbo@bayour.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2698
2014-09-13 18:13:00 +04:00
.ad
.RS 12n
OpenZFS 9426 - metaslab size can exceed offset addressable by spacemap Authored by: Don Brady <don.brady@delphix.com> Reviewed by: Paul Dagnelie <pcd@delphix.com> Reviewed by: Matt Ahrens <matt@delphix.com> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Dan McDonald <danmcd@joyent.com> OpenZFS-issue: https://www.illumos.org/issues/9426 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/f1c88afb1 Closes #7700
2017-08-12 00:28:17 +03:00
When a vdev is added target this number of metaslabs per top-level vdev.
Illumos 5161 - add tunable for number of metaslabs per vdev 5161 add tunable for number of metaslabs per vdev Reviewed by: Alex Reece <alex.reece@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Paul Dagnelie <paul.dagnelie@delphix.com> Reviewed by: Saso Kiselkov <skiselkov.ml@gmail.com> Reviewed by: Richard Elling <richard.elling@gmail.com> Approved by: Richard Lowe <richlowe@richlowe.net> References: https://www.illumos.org/issues/5161 https://github.com/illumos/illumos-gate/commit/bf3e216 Ported by: Turbo Fredriksson <turbo@bayour.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2698
2014-09-13 18:13:00 +04:00
.sp
Default value: \fB200\fR.
.RE
OpenZFS 9166 - zfs storage pool checkpoint Details about the motivation of this feature and its usage can be found in this blogpost: https://sdimitro.github.io/post/zpool-checkpoint/ A lightning talk of this feature can be found here: https://www.youtube.com/watch?v=fPQA8K40jAM Implementation details can be found in big block comment of spa_checkpoint.c Side-changes that are relevant to this commit but not explained elsewhere: * renames members of "struct metaslab trees to be shorter without losing meaning * space_map_{alloc,truncate}() accept a block size as a parameter. The reason is that in the current state all space maps that we allocate through the DMU use a global tunable (space_map_blksz) which defauls to 4KB. This is ok for metaslab space maps in terms of bandwirdth since they are scattered all over the disk. But for other space maps this default is probably not what we want. Examples are device removal's vdev_obsolete_sm or vdev_chedkpoint_sm from this review. Both of these have a 1:1 relationship with each vdev and could benefit from a bigger block size. Porting notes: * The part of dsl_scan_sync() which handles async destroys has been moved into the new dsl_process_async_destroys() function. * Remove "VERIFY(!(flags & FWRITE))" in "kernel.c" so zhack can write to block device backed pools. * ZTS: * Fix get_txg() in zpool_sync_001_pos due to "checkpoint_txg". * Don't use large dd block sizes on /dev/urandom under Linux in checkpoint_capacity. * Adopt Delphix-OS's setting of 4 (spa_asize_inflation = SPA_DVAS_PER_BP + 1) for the checkpoint_capacity test to speed its attempts to fill the pool * Create the base and nested pools with sync=disabled to speed up the "setup" phase. * Clear labels in test pool between checkpoint tests to avoid duplicate pool issues. * The import_rewind_device_replaced test has been marked as "known to fail" for the reasons listed in its DISCLAIMER. * New module parameters: zfs_spa_discard_memory_limit, zfs_remove_max_bytes_pause (not documented - debugging only) vdev_max_ms_count (formerly metaslabs_per_vdev) vdev_min_ms_count Authored by: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: John Kennedy <john.kennedy@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Richard Lowe <richlowe@richlowe.net> Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Tim Chase <tim@chase2k.com> OpenZFS-issue: https://illumos.org/issues/9166 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/7159fdb8 Closes #7570
2016-12-17 01:11:29 +03:00
.sp
.ne 2
.na
\fBvdev_min_ms_count\fR (int)
.ad
.RS 12n
Minimum number of metaslabs to create in a top-level vdev.
.sp
Default value: \fB16\fR.
.RE
OpenZFS 9426 - metaslab size can exceed offset addressable by spacemap Authored by: Don Brady <don.brady@delphix.com> Reviewed by: Paul Dagnelie <pcd@delphix.com> Reviewed by: Matt Ahrens <matt@delphix.com> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Dan McDonald <danmcd@joyent.com> OpenZFS-issue: https://www.illumos.org/issues/9426 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/f1c88afb1 Closes #7700
2017-08-12 00:28:17 +03:00
.sp
.ne 2
.na
\fBvdev_ms_count_limit\fR (int)
.ad
.RS 12n
Practical upper limit of total metaslabs per top-level vdev.
.sp
Default value: \fB131,072\fR.
.RE
Illumos 4976-4984 - metaslab improvements 4976 zfs should only avoid writing to a failing non-redundant top-level vdev 4978 ztest fails in get_metaslab_refcount() 4979 extend free space histogram to device and pool 4980 metaslabs should have a fragmentation metric 4981 remove fragmented ops vector from block allocator 4982 space_map object should proactively upgrade when feature is enabled 4983 need to collect metaslab information via mdb 4984 device selection should use fragmentation metric Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Adam Leventhal <adam.leventhal@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Approved by: Garrett D'Amore <garrett@damore.org> References: https://www.illumos.org/issues/4976 https://www.illumos.org/issues/4978 https://www.illumos.org/issues/4979 https://www.illumos.org/issues/4980 https://www.illumos.org/issues/4981 https://www.illumos.org/issues/4982 https://www.illumos.org/issues/4983 https://www.illumos.org/issues/4984 https://github.com/illumos/illumos-gate/commit/2e4c998 Notes: The "zdb -M" option has been re-tasked to display the new metaslab fragmentation metric and the new "zdb -I" option is used to control the maximum number of in-flight I/Os. The new fragmentation metric is derived from the space map histogram which has been rolled up to the vdev and pool level and is presented to the user via "zpool list". Add a number of module parameters related to the new metaslab weighting logic. Ported by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2595
2014-07-20 00:19:24 +04:00
.sp
.ne 2
.na
\fBmetaslab_preload_enabled\fR (int)
.ad
.RS 12n
Enable metaslab group preloading.
.sp
Use \fB1\fR for yes (default) and \fB0\fR for no.
.RE
.sp
.ne 2
.na
\fBmetaslab_lba_weighting_enabled\fR (int)
.ad
.RS 12n
Give more weight to metaslabs with lower LBAs, assuming they have
greater bandwidth as is typically the case on a modern constant
angular velocity disk drive.
.sp
Use \fB1\fR for yes (default) and \fB0\fR for no.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
.ne 2
.na
\fBspa_config_path\fR (charp)
.ad
.RS 12n
SPA config file
.sp
Default value: \fB/etc/zfs/zpool.cache\fR.
.RE
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 07:01:20 +04:00
.sp
.ne 2
.na
\fBspa_asize_inflation\fR (int)
.ad
.RS 12n
Multiplication factor used to estimate actual disk consumption from the
size of data being written. The default value is a worst case estimate,
but lower values may be valid for a given pool depending on its
configuration. Pool administrators who understand the factors involved
may wish to specify a more realistic inflation factor, particularly if
they operate close to quota or capacity limits.
.sp
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Default value: \fB24\fR.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 07:01:20 +04:00
.RE
OpenZFS 9075 - Improve ZFS pool import/load process and corrupted pool recovery Some work has been done lately to improve the debugability of the ZFS pool load (and import) process. This includes: 7638 Refactor spa_load_impl into several functions 8961 SPA load/import should tell us why it failed 7277 zdb should be able to print zfs_dbgmsg's To iterate on top of that, there's a few changes that were made to make the import process more resilient and crash free. One of the first tasks during the pool load process is to parse a config provided from userland that describes what devices the pool is composed of. A vdev tree is generated from that config, and then all the vdevs are opened. The Meta Object Set (MOS) of the pool is accessed, and several metadata objects that are necessary to load the pool are read. The exact configuration of the pool is also stored inside the MOS. Since the configuration provided from userland is external and might not accurately describe the vdev tree of the pool at the txg that is being loaded, it cannot be relied upon to safely operate the pool. For that reason, the configuration in the MOS is read early on. In the past, the two configurations were compared together and if there was a mismatch then the load process was aborted and an error was returned. The latter was a good way to ensure a pool does not get corrupted, however it made the pool load process needlessly fragile in cases where the vdev configuration changed or the userland configuration was outdated. Since the MOS is stored in 3 copies, the configuration provided by userland doesn't have to be perfect in order to read its contents. Hence, a new approach has been adopted: The pool is first opened with the untrusted userland configuration just so that the real configuration can be read from the MOS. The trusted MOS configuration is then used to generate a new vdev tree and the pool is re-opened. When the pool is opened with an untrusted configuration, writes are disabled to avoid accidentally damaging it. During reads, some sanity checks are performed on block pointers to see if each DVA points to a known vdev; when the configuration is untrusted, instead of panicking the system if those checks fail we simply avoid issuing reads to the invalid DVAs. This new two-step pool load process now allows rewinding pools accross vdev tree changes such as device replacement, addition, etc. Loading a pool from an external config file in a clustering environment also becomes much safer now since the pool will import even if the config is outdated and didn't, for instance, register a recent device addition. With this code in place, it became relatively easy to implement a long-sought-after feature: the ability to import a pool with missing top level (i.e. non-redundant) devices. Note that since this almost guarantees some loss of data, this feature is for now restricted to a read-only import. Porting notes (ZTS): * Fix 'make dist' target in zpool_import * The maximum path length allowed by tar is 99 characters. Several of the new test cases exceeded this limit resulting in them not being included in the tarball. Shorten the names slightly. * Set/get tunables using accessor functions. * Get last synced txg via the "zfs_txg_history" mechanism. * Clear zinject handlers in cleanup for import_cache_device_replaced and import_rewind_device_replaced in order that the zpool can be exported if there is an error. * Increase FILESIZE to 8G in zfs-test.sh to allow for a larger ext4 file system to be created on ZFS_DISK2. Also, there's no need to partition ZFS_DISK2 at all. The partitioning had already been disabled for multipath devices. Among other things, the partitioning steals some space from the ext4 file system, makes it difficult to accurately calculate the paramters to parted and can make some of the tests fail. * Increase FS_SIZE and FILE_SIZE in the zpool_import test configuration now that FILESIZE is larger. * Write more data in order that device evacuation take lonnger in a couple tests. * Use mkdir -p to avoid errors when the directory already exists. * Remove use of sudo in import_rewind_config_changed. Authored by: Pavel Zakharov <pavel.zakharov@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Andrew Stormont <andyjstormont@gmail.com> Approved by: Hans Rosenfeld <rosenfeld@grumpf.hope-2000.org> Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Tim Chase <tim@chase2k.com> OpenZFS-issue: https://illumos.org/issues/9075 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/619c0123 Closes #7459
2016-07-22 17:39:36 +03:00
.sp
.ne 2
.na
\fBspa_load_print_vdev_tree\fR (int)
.ad
.RS 12n
Whether to print the vdev tree in the debugging message buffer during pool import.
Use 0 to disable and 1 to enable.
.sp
Default value: \fB0\fR.
.RE
Illumos 4970-4974 - extreme rewind enhancements 4970 need controls on i/o issued by zpool import -XF 4971 zpool import -T should accept hex values 4972 zpool import -T implies extreme rewind, and thus a scrub 4973 spa_load_retry retries the same txg 4974 spa_load_verify() reads all data twice Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Dan McDonald <danmcd@omniti.com> Reviewed by: George Wilson <george.wilson@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> References: https://www.illumos.org/issues/4970 https://www.illumos.org/issues/4971 https://www.illumos.org/issues/4972 https://www.illumos.org/issues/4973 https://www.illumos.org/issues/4974 https://github.com/illumos/illumos-gate/commit/e42d205 Notes: This set of patches adds a set of tunable parameters for the "extreme rewind" mode of pool import which allows control over the traversal performed during such an import. Ported by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2598
2014-07-15 22:58:41 +04:00
.sp
.ne 2
.na
\fBspa_load_verify_data\fR (int)
.ad
.RS 12n
Whether to traverse data blocks during an "extreme rewind" (\fB-X\fR)
import. Use 0 to disable and 1 to enable.
An extreme rewind import normally performs a full traversal of all
blocks in the pool for verification. If this parameter is set to 0,
the traversal skips non-metadata blocks. It can be toggled once the
import has started to stop or start the traversal of non-metadata blocks.
.sp
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Default value: \fB1\fR.
Illumos 4970-4974 - extreme rewind enhancements 4970 need controls on i/o issued by zpool import -XF 4971 zpool import -T should accept hex values 4972 zpool import -T implies extreme rewind, and thus a scrub 4973 spa_load_retry retries the same txg 4974 spa_load_verify() reads all data twice Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Dan McDonald <danmcd@omniti.com> Reviewed by: George Wilson <george.wilson@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> References: https://www.illumos.org/issues/4970 https://www.illumos.org/issues/4971 https://www.illumos.org/issues/4972 https://www.illumos.org/issues/4973 https://www.illumos.org/issues/4974 https://github.com/illumos/illumos-gate/commit/e42d205 Notes: This set of patches adds a set of tunable parameters for the "extreme rewind" mode of pool import which allows control over the traversal performed during such an import. Ported by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2598
2014-07-15 22:58:41 +04:00
.RE
.sp
.ne 2
.na
\fBspa_load_verify_metadata\fR (int)
.ad
.RS 12n
Whether to traverse blocks during an "extreme rewind" (\fB-X\fR)
pool import. Use 0 to disable and 1 to enable.
An extreme rewind import normally performs a full traversal of all
Correct typo in spa_load_verify_metadata docs Signed-off-by: Richard Laager <rlaager@wiktel.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4471
2016-03-29 01:13:42 +03:00
blocks in the pool for verification. If this parameter is set to 0,
Illumos 4970-4974 - extreme rewind enhancements 4970 need controls on i/o issued by zpool import -XF 4971 zpool import -T should accept hex values 4972 zpool import -T implies extreme rewind, and thus a scrub 4973 spa_load_retry retries the same txg 4974 spa_load_verify() reads all data twice Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Dan McDonald <danmcd@omniti.com> Reviewed by: George Wilson <george.wilson@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> References: https://www.illumos.org/issues/4970 https://www.illumos.org/issues/4971 https://www.illumos.org/issues/4972 https://www.illumos.org/issues/4973 https://www.illumos.org/issues/4974 https://github.com/illumos/illumos-gate/commit/e42d205 Notes: This set of patches adds a set of tunable parameters for the "extreme rewind" mode of pool import which allows control over the traversal performed during such an import. Ported by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2598
2014-07-15 22:58:41 +04:00
the traversal is not performed. It can be toggled once the import has
started to stop or start the traversal.
.sp
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Default value: \fB1\fR.
Illumos 4970-4974 - extreme rewind enhancements 4970 need controls on i/o issued by zpool import -XF 4971 zpool import -T should accept hex values 4972 zpool import -T implies extreme rewind, and thus a scrub 4973 spa_load_retry retries the same txg 4974 spa_load_verify() reads all data twice Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Dan McDonald <danmcd@omniti.com> Reviewed by: George Wilson <george.wilson@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> References: https://www.illumos.org/issues/4970 https://www.illumos.org/issues/4971 https://www.illumos.org/issues/4972 https://www.illumos.org/issues/4973 https://www.illumos.org/issues/4974 https://github.com/illumos/illumos-gate/commit/e42d205 Notes: This set of patches adds a set of tunable parameters for the "extreme rewind" mode of pool import which allows control over the traversal performed during such an import. Ported by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2598
2014-07-15 22:58:41 +04:00
.RE
.sp
.ne 2
.na
\fBspa_load_verify_maxinflight\fR (int)
.ad
.RS 12n
Maximum concurrent I/Os during the traversal performed during an "extreme
rewind" (\fB-X\fR) pool import.
.sp
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Default value: \fB10000\fR.
Illumos 4970-4974 - extreme rewind enhancements 4970 need controls on i/o issued by zpool import -XF 4971 zpool import -T should accept hex values 4972 zpool import -T implies extreme rewind, and thus a scrub 4973 spa_load_retry retries the same txg 4974 spa_load_verify() reads all data twice Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Dan McDonald <danmcd@omniti.com> Reviewed by: George Wilson <george.wilson@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> References: https://www.illumos.org/issues/4970 https://www.illumos.org/issues/4971 https://www.illumos.org/issues/4972 https://www.illumos.org/issues/4973 https://www.illumos.org/issues/4974 https://github.com/illumos/illumos-gate/commit/e42d205 Notes: This set of patches adds a set of tunable parameters for the "extreme rewind" mode of pool import which allows control over the traversal performed during such an import. Ported by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2598
2014-07-15 22:58:41 +04:00
.RE
Add spa_slop_shift module option Allow for easy turning of a pools reserved free space. Previous versions of ZFS (v0.6.4 and earlier) held 1/64 of the pools capacity in reserve. Commits 3d45fdd and 0c60cc3 increased this to 1/32. Setting spa_slop_shift=6 will restore the previous default setting. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #3724
2015-09-01 19:45:10 +03:00
.sp
.ne 2
.na
\fBspa_slop_shift\fR (int)
.ad
.RS 12n
Normally, we don't allow the last 3.2% (1/(2^spa_slop_shift)) of space
in the pool to be consumed. This ensures that we don't run the pool
completely out of space, due to unaccounted changes (e.g. to the MOS).
It also limits the worst-case time to allocate space. If we have
less than this amount of free space, most ZPL operations (e.g. write,
create) will return ENOSPC.
.sp
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Default value: \fB5\fR.
Add spa_slop_shift module option Allow for easy turning of a pools reserved free space. Previous versions of ZFS (v0.6.4 and earlier) held 1/64 of the pools capacity in reserve. Commits 3d45fdd and 0c60cc3 increased this to 1/32. Setting spa_slop_shift=6 will restore the previous default setting. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #3724
2015-09-01 19:45:10 +03:00
.RE
OpenZFS 9486 - reduce memory used by device removal on fragmented pools Device removal allocates a new location for each allocated segment on the disk that's being removed. Each allocation results in one entry in the mapping table, which maps from old location + length to new location. When a fragmented disk is removed, this can result in a large number of mapping entries, and thus a large amount of memory consumed by the mapping table. In the worst real-world cases, we've seen around 1GB of RAM per 1TB of storage removed. We can improve on this situation by allocating larger segments, which span across both allocated and free regions of the device being removed. By including free regions in the allocation (and thus mapping), we reduce the number of mapping entries. For example, if we have a 4K allocation followed by 1K free and then 4K allocated, we would allocate 4+1+4 = 9KB, and then move the entire region (including allocated and free parts). In this case we used one mapping where previously we would have used two, but often the ratio is much higher (up to 20:1 in real-world use). We then need to mark the regions that were free on the removing device as free in the new locations, and also obsolete in the mapping entry. This method preserves the fragmentation of the removing device, rather than consolidating its allocated space into a small number of chunks where possible. But it results in drastic reduction of memory used by the mapping table - around 20x in the most-fragmented cases. In the most fragmented real-world cases, this reduces memory used by the mapping from ~1GB to ~50MB of RAM per 1TB of storage removed. Less fragmented cases will typically also see around 50-100MB of RAM per 1TB of storage. Porting notes: * Add the following as module parameters: * zfs_condense_indirect_vdevs_enable * zfs_condense_max_obsolete_bytes * Document the following module parameters: * zfs_condense_indirect_vdevs_enable * zfs_condense_max_obsolete_bytes * zfs_condense_min_mapping_bytes Authored by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Tim Chase <tim@chase2k.com> OpenZFS-issue: https://illumos.org/issues/9486 OpenZFS-commit: https://github.com/ahrens/illumos/commit/07152e142e44c External-issue: DLPX-57962 Closes #7536
2018-02-27 02:33:55 +03:00
.sp
.ne 2
.na
\fBvdev_removal_max_span\fR (int)
.ad
.RS 12n
During top-level vdev removal, chunks of data are copied from the vdev
which may include free space in order to trade bandwidth for IOPS.
This parameter determines the maximum span of free space (in bytes)
which will be included as "unnecessary" data in a chunk of copied data.
The default value here was chosen to align with
\fBzfs_vdev_read_gap_limit\fR, which is a similar concept when doing
regular reads (but there's no reason it has to be the same).
.sp
Default value: \fB32,768\fR.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
.ne 2
.na
\fBzfetch_array_rd_sz\fR (ulong)
.ad
.RS 12n
Expand the description of scan-related and other parameters. Document that the scan-related parameters are, in fact, applicable only to scrub and/or resilver operations as appropriate. Expand a few of the prefetch-related descriptions. Add clarification to other module parameters. Signed-off-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2361
2014-06-04 16:23:31 +04:00
If prefetching is enabled, disable prefetching for reads larger than this size.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Default value: \fB1,048,576\fR.
.RE
.sp
.ne 2
.na
Illumos 5987 - zfs prefetch code needs work 5987 zfs prefetch code needs work Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Paul Dagnelie <pcd@delphix.com> Approved by: Gordon Ross <gordon.ross@nexenta.com> References: https://www.illumos.org/issues/5987 zfs prefetch code needs work illumos/illumos-gate@cf6106c 5987 zfs prefetch code needs work Porting notes: - [module/zfs/dbuf.c] - 5f6d0b6 Handle block pointers with a corrupt logical size - [module/zfs/dmu_zfetch.c] - c65aa5b Fix gcc missing parenthesis warnings - 428870f Update core ZFS code from build 121 to build 141. - 79c76d5 Change KM_PUSHPAGE -> KM_SLEEP - b8d06fc Switch KM_SLEEP to KM_PUSHPAGE - Account for ISO C90 - mixed declarations and code - warnings - Module parameters (new/changed): - Replaced zfetch_block_cap with zfetch_max_distance (Max bytes to prefetch per stream (default 8MB; 8 * 1024 * 1024)) - Preserved zfs_prefetch_disable as 'int' for consistency with existing Linux module options. - [include/sys/trace_arc.h] - Added new tracepoints - DEFINE_ARC_BUF_HDR_EVENT(zfs_arc__sync__wait__for__async); - DEFINE_ARC_BUF_HDR_EVENT(zfs_arc__demand__hit__predictive__prefetch); - [man/man5/zfs-module-parameters.5] - Updated man page Ported-by: kernelOfTruth kerneloftruth@gmail.com Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2015-12-27 00:10:31 +03:00
\fBzfetch_max_distance\fR (uint)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.ad
.RS 12n
Illumos 5987 - zfs prefetch code needs work 5987 zfs prefetch code needs work Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Paul Dagnelie <pcd@delphix.com> Approved by: Gordon Ross <gordon.ross@nexenta.com> References: https://www.illumos.org/issues/5987 zfs prefetch code needs work illumos/illumos-gate@cf6106c 5987 zfs prefetch code needs work Porting notes: - [module/zfs/dbuf.c] - 5f6d0b6 Handle block pointers with a corrupt logical size - [module/zfs/dmu_zfetch.c] - c65aa5b Fix gcc missing parenthesis warnings - 428870f Update core ZFS code from build 121 to build 141. - 79c76d5 Change KM_PUSHPAGE -> KM_SLEEP - b8d06fc Switch KM_SLEEP to KM_PUSHPAGE - Account for ISO C90 - mixed declarations and code - warnings - Module parameters (new/changed): - Replaced zfetch_block_cap with zfetch_max_distance (Max bytes to prefetch per stream (default 8MB; 8 * 1024 * 1024)) - Preserved zfs_prefetch_disable as 'int' for consistency with existing Linux module options. - [include/sys/trace_arc.h] - Added new tracepoints - DEFINE_ARC_BUF_HDR_EVENT(zfs_arc__sync__wait__for__async); - DEFINE_ARC_BUF_HDR_EVENT(zfs_arc__demand__hit__predictive__prefetch); - [man/man5/zfs-module-parameters.5] - Updated man page Ported-by: kernelOfTruth kerneloftruth@gmail.com Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2015-12-27 00:10:31 +03:00
Max bytes to prefetch per stream (default 8MB).
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Illumos 5987 - zfs prefetch code needs work 5987 zfs prefetch code needs work Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Paul Dagnelie <pcd@delphix.com> Approved by: Gordon Ross <gordon.ross@nexenta.com> References: https://www.illumos.org/issues/5987 zfs prefetch code needs work illumos/illumos-gate@cf6106c 5987 zfs prefetch code needs work Porting notes: - [module/zfs/dbuf.c] - 5f6d0b6 Handle block pointers with a corrupt logical size - [module/zfs/dmu_zfetch.c] - c65aa5b Fix gcc missing parenthesis warnings - 428870f Update core ZFS code from build 121 to build 141. - 79c76d5 Change KM_PUSHPAGE -> KM_SLEEP - b8d06fc Switch KM_SLEEP to KM_PUSHPAGE - Account for ISO C90 - mixed declarations and code - warnings - Module parameters (new/changed): - Replaced zfetch_block_cap with zfetch_max_distance (Max bytes to prefetch per stream (default 8MB; 8 * 1024 * 1024)) - Preserved zfs_prefetch_disable as 'int' for consistency with existing Linux module options. - [include/sys/trace_arc.h] - Added new tracepoints - DEFINE_ARC_BUF_HDR_EVENT(zfs_arc__sync__wait__for__async); - DEFINE_ARC_BUF_HDR_EVENT(zfs_arc__demand__hit__predictive__prefetch); - [man/man5/zfs-module-parameters.5] - Updated man page Ported-by: kernelOfTruth kerneloftruth@gmail.com Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2015-12-27 00:10:31 +03:00
Default value: \fB8,388,608\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.RE
.sp
.ne 2
.na
\fBzfetch_max_streams\fR (uint)
.ad
.RS 12n
Expand the description of scan-related and other parameters. Document that the scan-related parameters are, in fact, applicable only to scrub and/or resilver operations as appropriate. Expand a few of the prefetch-related descriptions. Add clarification to other module parameters. Signed-off-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2361
2014-06-04 16:23:31 +04:00
Max number of streams per zfetch (prefetch streams per file).
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Default value: \fB8\fR.
.RE
.sp
.ne 2
.na
\fBzfetch_min_sec_reap\fR (uint)
.ad
.RS 12n
Expand the description of scan-related and other parameters. Document that the scan-related parameters are, in fact, applicable only to scrub and/or resilver operations as appropriate. Expand a few of the prefetch-related descriptions. Add clarification to other module parameters. Signed-off-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2361
2014-06-04 16:23:31 +04:00
Min time before an active prefetch stream can be reclaimed
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Default value: \fB2\fR.
.RE
Limit the amount of dnode metadata in the ARC Metadata-intensive workloads can cause the ARC to become permanently filled with dnode_t objects as they're pinned by the VFS layer. Subsequent data-intensive workloads may only benefit from about 25% of the potential ARC (arc_c_max - arc_meta_limit). In order to help track metadata usage more precisely, the other_size metadata arcstat has replaced with dbuf_size, dnode_size and bonus_size. The new zfs_arc_dnode_limit tunable, which defaults to 10% of zfs_arc_meta_limit, defines the minimum number of bytes which is desirable to be consumed by dnodes. Attempts to evict non-metadata will trigger async prune tasks if the space used by dnodes exceeds this limit. The new zfs_arc_dnode_reduce_percent tunable specifies the amount by which the excess dnode space is attempted to be pruned as a percentage of the amount by which zfs_arc_dnode_limit is being exceeded. By default, it tries to unpin 10% of the dnodes. The problem of dnode metadata pinning was observed with the following testing procedure (in this example, zfs_arc_max is set to 4GiB): - Create a large number of small files until arc_meta_used exceeds arc_meta_limit (3GiB with default tuning) and arc_prune starts increasing. - Create a 3GiB file with dd. Observe arc_mata_used. It will still be around 3GiB. - Repeatedly read the 3GiB file and observe arc_meta_limit as before. It will continue to stay around 3GiB. With this modification, space for the 3GiB file is gradually made available as subsequent demands on the ARC are made. The previous behavior can be restored by setting zfs_arc_dnode_limit to the same value as the zfs_arc_meta_limit. Signed-off-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #4345 Issue #4512 Issue #4773 Closes #4858
2016-07-13 15:42:40 +03:00
.sp
.ne 2
.na
\fBzfs_arc_dnode_limit\fR (ulong)
.ad
.RS 12n
When the number of bytes consumed by dnodes in the ARC exceeds this number of
Add zfs_arc_meta_limit_percent tunable ARC will evict meta buffers that exceed the arc_meta_limit. Before a further investigating on whether we should take special protection on meta buffers, this tunable make arc_meta_limit adjustable for different workloads. People can set zfs_arc_meta_limit_percent to any value while insmod zfs.ko, so some range check is added to guarantee a suitable arc_meta_limit. Suggested by Tim Chase, zfs_arc_dnode_limit is changed to a percent-style tunable as well. Signed-off-by: GeLiXin <ge.lixin@zte.com.cn> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4957
2016-08-11 06:15:37 +03:00
bytes, try to unpin some of it in response to demand for non-metadata. This
Fix manual description of zfs_arc_dnode_limit In arc_evict_state() we start pruning when arc_dnode_size > arc_dnode_limit, i.e. arc_dnode_limit is a ceiling rather than a floor. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Chris Dunlop <chris@onthe.net.au> Closes #6228
2017-06-14 23:23:02 +03:00
value acts as a ceiling to the amount of dnode metadata, and defaults to 0 which
Add zfs_arc_meta_limit_percent tunable ARC will evict meta buffers that exceed the arc_meta_limit. Before a further investigating on whether we should take special protection on meta buffers, this tunable make arc_meta_limit adjustable for different workloads. People can set zfs_arc_meta_limit_percent to any value while insmod zfs.ko, so some range check is added to guarantee a suitable arc_meta_limit. Suggested by Tim Chase, zfs_arc_dnode_limit is changed to a percent-style tunable as well. Signed-off-by: GeLiXin <ge.lixin@zte.com.cn> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4957
2016-08-11 06:15:37 +03:00
indicates that a percent which is based on \fBzfs_arc_dnode_limit_percent\fR of
the ARC meta buffers that may be used for dnodes.
Limit the amount of dnode metadata in the ARC Metadata-intensive workloads can cause the ARC to become permanently filled with dnode_t objects as they're pinned by the VFS layer. Subsequent data-intensive workloads may only benefit from about 25% of the potential ARC (arc_c_max - arc_meta_limit). In order to help track metadata usage more precisely, the other_size metadata arcstat has replaced with dbuf_size, dnode_size and bonus_size. The new zfs_arc_dnode_limit tunable, which defaults to 10% of zfs_arc_meta_limit, defines the minimum number of bytes which is desirable to be consumed by dnodes. Attempts to evict non-metadata will trigger async prune tasks if the space used by dnodes exceeds this limit. The new zfs_arc_dnode_reduce_percent tunable specifies the amount by which the excess dnode space is attempted to be pruned as a percentage of the amount by which zfs_arc_dnode_limit is being exceeded. By default, it tries to unpin 10% of the dnodes. The problem of dnode metadata pinning was observed with the following testing procedure (in this example, zfs_arc_max is set to 4GiB): - Create a large number of small files until arc_meta_used exceeds arc_meta_limit (3GiB with default tuning) and arc_prune starts increasing. - Create a 3GiB file with dd. Observe arc_mata_used. It will still be around 3GiB. - Repeatedly read the 3GiB file and observe arc_meta_limit as before. It will continue to stay around 3GiB. With this modification, space for the 3GiB file is gradually made available as subsequent demands on the ARC are made. The previous behavior can be restored by setting zfs_arc_dnode_limit to the same value as the zfs_arc_meta_limit. Signed-off-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #4345 Issue #4512 Issue #4773 Closes #4858
2016-07-13 15:42:40 +03:00
See also \fBzfs_arc_meta_prune\fR which serves a similar purpose but is used
when the amount of metadata in the ARC exceeds \fBzfs_arc_meta_limit\fR rather
than in response to overall demand for non-metadata.
.sp
Add zfs_arc_meta_limit_percent tunable ARC will evict meta buffers that exceed the arc_meta_limit. Before a further investigating on whether we should take special protection on meta buffers, this tunable make arc_meta_limit adjustable for different workloads. People can set zfs_arc_meta_limit_percent to any value while insmod zfs.ko, so some range check is added to guarantee a suitable arc_meta_limit. Suggested by Tim Chase, zfs_arc_dnode_limit is changed to a percent-style tunable as well. Signed-off-by: GeLiXin <ge.lixin@zte.com.cn> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4957
2016-08-11 06:15:37 +03:00
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
\fBzfs_arc_dnode_limit_percent\fR (ulong)
.ad
.RS 12n
Percentage that can be consumed by dnodes of ARC meta buffers.
.sp
See also \fBzfs_arc_dnode_limit\fR which serves a similar purpose but has a
higher priority if set to nonzero value.
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 22:51:11 +03:00
Default value: \fB10\fR%.
Limit the amount of dnode metadata in the ARC Metadata-intensive workloads can cause the ARC to become permanently filled with dnode_t objects as they're pinned by the VFS layer. Subsequent data-intensive workloads may only benefit from about 25% of the potential ARC (arc_c_max - arc_meta_limit). In order to help track metadata usage more precisely, the other_size metadata arcstat has replaced with dbuf_size, dnode_size and bonus_size. The new zfs_arc_dnode_limit tunable, which defaults to 10% of zfs_arc_meta_limit, defines the minimum number of bytes which is desirable to be consumed by dnodes. Attempts to evict non-metadata will trigger async prune tasks if the space used by dnodes exceeds this limit. The new zfs_arc_dnode_reduce_percent tunable specifies the amount by which the excess dnode space is attempted to be pruned as a percentage of the amount by which zfs_arc_dnode_limit is being exceeded. By default, it tries to unpin 10% of the dnodes. The problem of dnode metadata pinning was observed with the following testing procedure (in this example, zfs_arc_max is set to 4GiB): - Create a large number of small files until arc_meta_used exceeds arc_meta_limit (3GiB with default tuning) and arc_prune starts increasing. - Create a 3GiB file with dd. Observe arc_mata_used. It will still be around 3GiB. - Repeatedly read the 3GiB file and observe arc_meta_limit as before. It will continue to stay around 3GiB. With this modification, space for the 3GiB file is gradually made available as subsequent demands on the ARC are made. The previous behavior can be restored by setting zfs_arc_dnode_limit to the same value as the zfs_arc_meta_limit. Signed-off-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #4345 Issue #4512 Issue #4773 Closes #4858
2016-07-13 15:42:40 +03:00
.RE
.sp
.ne 2
.na
\fBzfs_arc_dnode_reduce_percent\fR (ulong)
.ad
.RS 12n
Percentage of ARC dnodes to try to scan in response to demand for non-metadata
Fix man page formatting in zfs-module-parameters Bold and Normal codes were mixed up in a few places resulting in bad highlighting. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: DHE <git@dehacked.net> Closes #5397
2016-11-15 04:03:57 +03:00
when the number of bytes consumed by dnodes exceeds \fBzfs_arc_dnode_limit\fR.
Limit the amount of dnode metadata in the ARC Metadata-intensive workloads can cause the ARC to become permanently filled with dnode_t objects as they're pinned by the VFS layer. Subsequent data-intensive workloads may only benefit from about 25% of the potential ARC (arc_c_max - arc_meta_limit). In order to help track metadata usage more precisely, the other_size metadata arcstat has replaced with dbuf_size, dnode_size and bonus_size. The new zfs_arc_dnode_limit tunable, which defaults to 10% of zfs_arc_meta_limit, defines the minimum number of bytes which is desirable to be consumed by dnodes. Attempts to evict non-metadata will trigger async prune tasks if the space used by dnodes exceeds this limit. The new zfs_arc_dnode_reduce_percent tunable specifies the amount by which the excess dnode space is attempted to be pruned as a percentage of the amount by which zfs_arc_dnode_limit is being exceeded. By default, it tries to unpin 10% of the dnodes. The problem of dnode metadata pinning was observed with the following testing procedure (in this example, zfs_arc_max is set to 4GiB): - Create a large number of small files until arc_meta_used exceeds arc_meta_limit (3GiB with default tuning) and arc_prune starts increasing. - Create a 3GiB file with dd. Observe arc_mata_used. It will still be around 3GiB. - Repeatedly read the 3GiB file and observe arc_meta_limit as before. It will continue to stay around 3GiB. With this modification, space for the 3GiB file is gradually made available as subsequent demands on the ARC are made. The previous behavior can be restored by setting zfs_arc_dnode_limit to the same value as the zfs_arc_meta_limit. Signed-off-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #4345 Issue #4512 Issue #4773 Closes #4858
2016-07-13 15:42:40 +03:00
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 22:51:11 +03:00
Default value: \fB10\fR% of the number of dnodes in the ARC.
Limit the amount of dnode metadata in the ARC Metadata-intensive workloads can cause the ARC to become permanently filled with dnode_t objects as they're pinned by the VFS layer. Subsequent data-intensive workloads may only benefit from about 25% of the potential ARC (arc_c_max - arc_meta_limit). In order to help track metadata usage more precisely, the other_size metadata arcstat has replaced with dbuf_size, dnode_size and bonus_size. The new zfs_arc_dnode_limit tunable, which defaults to 10% of zfs_arc_meta_limit, defines the minimum number of bytes which is desirable to be consumed by dnodes. Attempts to evict non-metadata will trigger async prune tasks if the space used by dnodes exceeds this limit. The new zfs_arc_dnode_reduce_percent tunable specifies the amount by which the excess dnode space is attempted to be pruned as a percentage of the amount by which zfs_arc_dnode_limit is being exceeded. By default, it tries to unpin 10% of the dnodes. The problem of dnode metadata pinning was observed with the following testing procedure (in this example, zfs_arc_max is set to 4GiB): - Create a large number of small files until arc_meta_used exceeds arc_meta_limit (3GiB with default tuning) and arc_prune starts increasing. - Create a 3GiB file with dd. Observe arc_mata_used. It will still be around 3GiB. - Repeatedly read the 3GiB file and observe arc_meta_limit as before. It will continue to stay around 3GiB. With this modification, space for the 3GiB file is gradually made available as subsequent demands on the ARC are made. The previous behavior can be restored by setting zfs_arc_dnode_limit to the same value as the zfs_arc_meta_limit. Signed-off-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #4345 Issue #4512 Issue #4773 Closes #4858
2016-07-13 15:42:40 +03:00
.RE
Illumos 5034 - ARC's buf_hash_table is too small 5034 ARC's buf_hash_table is too small Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Saso Kiselkov <skiselkov.ml@gmail.com> Reviewed by: Richard Elling <richard.elling@gmail.com> Approved by: Gordon Ross <gwr@nexenta.com> References: https://www.illumos.org/issues/5034 https://github.com/illumos/illumos-gate/commit/63e911b Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2615
2014-08-20 21:09:40 +04:00
.sp
.ne 2
.na
\fBzfs_arc_average_blocksize\fR (int)
.ad
.RS 12n
The ARC's buffer hash table is sized based on the assumption of an average
block size of \fBzfs_arc_average_blocksize\fR (default 8K). This works out
to roughly 1MB of hash table per 1GB of physical memory with 8-byte pointers.
For configurations with a known larger average block size this value can be
increased to reduce the memory footprint.
.sp
Default value: \fB8192\fR.
.RE
Illumos 5497 - lock contention on arcs_mtx Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Richard Elling <richard.elling@richardelling.com> Approved by: Dan McDonald <danmcd@omniti.com> Porting notes and other significant code changes: The illumos 5368 patch (ARC should cache more metadata), which was never picked up by ZoL, is mostly reverted by this patch. Since ZoL relies on the kernel asynchronously calling the shrinker to actually reap memory, the shrinker wakes up arc_reclaim_waiters_cv every time it runs. The arc_adapt_thread() function no longer calls arc_do_user_evicts() since the newly-added arc_user_evicts_thread() calls it periodically. Notable conflicting ZoL commits which conflicted with this patch or whose effects are either duplicated or un-done by this patch: 302f753 - Integrate ARC more tightly with Linux 39e055c - Adjust arc_p based on "bytes" in arc_shrink f521ce1 - Allow "arc_p" to drop to zero or grow to "arc_c" 77765b5 - Remove "arc_meta_used" from arc_adjust calculation 94520ca - Prune metadata from ghost lists in arc_adjust_meta Trace support for multilist_insert() and multilist_remove() has been added and produces the following output: fio-12498 [077] .... 112936.448324: zfs_multilist__insert: ml { offset 240 numsublists 80 sublistidx 63 } fio-12498 [077] .... 112936.448347: zfs_multilist__remove: ml { offset 240 numsublists 80 sublistidx 29 } The following arcstats have been removed: recycle_miss - Used by arcstat.py and arc_summary.py, both of which have been updated appropriately. l2_writes_hdr_miss The following arcstats have been added: evict_not_enough - Number of times arc_evict_state() was unable to evict enough buffers to reach its target amount. evict_l2_skip - Number of times arc_evict_hdr() skipped eviction because it was being written to the l2arc. l2_writes_lock_retry - Replaces l2_writes_hdr_miss. Number of times l2arc_write_done() failed to acquire hash_lock (and re-tries). arc_meta_min - Shows the value of the zfs_arc_meta_min module parameter (see below). The "index" column of the "dbuf" kstat has been removed since it doesn't have a direct analog in the new multilist scheme. Additional multilist- related stats could be added in the future but would likely require extensions to the mulilist API. The following module parameters have been added: zfs_arc_evict_batch_limit - Number of ARC headers to free per sub-list before moving on to the next sub-list. zfs_arc_meta_min - Enforce a floor on the amount of metadata in the ARC. zfs_arc_num_sublists_per_state - Number of multilist sub-lists per ARC state. zfs_arc_overflow_shift - Controls amount by which the ARC must exceed the target size to be considered "overflowing". Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov
2015-01-13 06:52:19 +03:00
.sp
.ne 2
.na
\fBzfs_arc_evict_batch_limit\fR (int)
.ad
.RS 12n
man: fix spelling mistakes in manual A few minor mistakes than should be fixed: zpool: compatability -> compatibility zfs: accessable -> accessible availible -> available zfs-events: availible -> available zfs-module-parameters: proceding -> proceeding Signed-off-by: Colin Ian King <colin.king@canonical.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #3544
2015-07-01 14:42:35 +03:00
Number ARC headers to evict per sub-list before proceeding to another sub-list.
Illumos 5497 - lock contention on arcs_mtx Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Richard Elling <richard.elling@richardelling.com> Approved by: Dan McDonald <danmcd@omniti.com> Porting notes and other significant code changes: The illumos 5368 patch (ARC should cache more metadata), which was never picked up by ZoL, is mostly reverted by this patch. Since ZoL relies on the kernel asynchronously calling the shrinker to actually reap memory, the shrinker wakes up arc_reclaim_waiters_cv every time it runs. The arc_adapt_thread() function no longer calls arc_do_user_evicts() since the newly-added arc_user_evicts_thread() calls it periodically. Notable conflicting ZoL commits which conflicted with this patch or whose effects are either duplicated or un-done by this patch: 302f753 - Integrate ARC more tightly with Linux 39e055c - Adjust arc_p based on "bytes" in arc_shrink f521ce1 - Allow "arc_p" to drop to zero or grow to "arc_c" 77765b5 - Remove "arc_meta_used" from arc_adjust calculation 94520ca - Prune metadata from ghost lists in arc_adjust_meta Trace support for multilist_insert() and multilist_remove() has been added and produces the following output: fio-12498 [077] .... 112936.448324: zfs_multilist__insert: ml { offset 240 numsublists 80 sublistidx 63 } fio-12498 [077] .... 112936.448347: zfs_multilist__remove: ml { offset 240 numsublists 80 sublistidx 29 } The following arcstats have been removed: recycle_miss - Used by arcstat.py and arc_summary.py, both of which have been updated appropriately. l2_writes_hdr_miss The following arcstats have been added: evict_not_enough - Number of times arc_evict_state() was unable to evict enough buffers to reach its target amount. evict_l2_skip - Number of times arc_evict_hdr() skipped eviction because it was being written to the l2arc. l2_writes_lock_retry - Replaces l2_writes_hdr_miss. Number of times l2arc_write_done() failed to acquire hash_lock (and re-tries). arc_meta_min - Shows the value of the zfs_arc_meta_min module parameter (see below). The "index" column of the "dbuf" kstat has been removed since it doesn't have a direct analog in the new multilist scheme. Additional multilist- related stats could be added in the future but would likely require extensions to the mulilist API. The following module parameters have been added: zfs_arc_evict_batch_limit - Number of ARC headers to free per sub-list before moving on to the next sub-list. zfs_arc_meta_min - Enforce a floor on the amount of metadata in the ARC. zfs_arc_num_sublists_per_state - Number of multilist sub-lists per ARC state. zfs_arc_overflow_shift - Controls amount by which the ARC must exceed the target size to be considered "overflowing". Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov
2015-01-13 06:52:19 +03:00
This batch-style operation prevents entire sub-lists from being evicted at once
but comes at a cost of additional unlocking and locking.
.sp
Default value: \fB10\fR.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
.ne 2
.na
\fBzfs_arc_grow_retry\fR (int)
.ad
.RS 12n
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 23:15:10 +03:00
If set to a non zero value, it will replace the arc_grow_retry value with this value.
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 04:27:01 +03:00
The arc_grow_retry value (default 5) is the number of seconds the ARC will wait before
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 23:15:10 +03:00
trying to resume growth after a memory pressure event.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 23:15:10 +03:00
Default value: \fB0\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.RE
.sp
.ne 2
.na
Update arc_memory_throttle() to check pageout This brings the behavior of arc_memory_throttle() back in sync with illumos. The updated memory throttling policy roughly goes like this: * Never throttle if more than 10% of memory is free. This threshold is configurable with the zfs_arc_lotsfree_percent module option. * Minimize any throttling of kswapd even when free memory is below the set threshold. Allow it to write out pages as quickly as possible to help alleviate the memory pressure. * Delay all other threads when free memory is below the set threshold in order to avoid compounding the memory pressure. Buffers will be evicted from the ARC to reduce the issue. The Linux specific zfs_arc_memory_throttle_disable module option has been removed in favor of the existing zfs_arc_lotsfree_percent tuning. Setting zfs_arc_lotsfree_percent=0 will have the same effect as zfs_arc_memory_throttle_disable and it was therefore redundant. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #3637
2015-07-28 21:30:00 +03:00
\fBzfs_arc_lotsfree_percent\fR (int)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.ad
.RS 12n
Update arc_memory_throttle() to check pageout This brings the behavior of arc_memory_throttle() back in sync with illumos. The updated memory throttling policy roughly goes like this: * Never throttle if more than 10% of memory is free. This threshold is configurable with the zfs_arc_lotsfree_percent module option. * Minimize any throttling of kswapd even when free memory is below the set threshold. Allow it to write out pages as quickly as possible to help alleviate the memory pressure. * Delay all other threads when free memory is below the set threshold in order to avoid compounding the memory pressure. Buffers will be evicted from the ARC to reduce the issue. The Linux specific zfs_arc_memory_throttle_disable module option has been removed in favor of the existing zfs_arc_lotsfree_percent tuning. Setting zfs_arc_lotsfree_percent=0 will have the same effect as zfs_arc_memory_throttle_disable and it was therefore redundant. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #3637
2015-07-28 21:30:00 +03:00
Throttle I/O when free system memory drops below this percentage of total
system memory. Setting this value to 0 will disable the throttle.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 22:51:11 +03:00
Default value: \fB10\fR%.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.RE
.sp
.ne 2
.na
Update arc_memory_throttle() to check pageout This brings the behavior of arc_memory_throttle() back in sync with illumos. The updated memory throttling policy roughly goes like this: * Never throttle if more than 10% of memory is free. This threshold is configurable with the zfs_arc_lotsfree_percent module option. * Minimize any throttling of kswapd even when free memory is below the set threshold. Allow it to write out pages as quickly as possible to help alleviate the memory pressure. * Delay all other threads when free memory is below the set threshold in order to avoid compounding the memory pressure. Buffers will be evicted from the ARC to reduce the issue. The Linux specific zfs_arc_memory_throttle_disable module option has been removed in favor of the existing zfs_arc_lotsfree_percent tuning. Setting zfs_arc_lotsfree_percent=0 will have the same effect as zfs_arc_memory_throttle_disable and it was therefore redundant. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #3637
2015-07-28 21:30:00 +03:00
\fBzfs_arc_max\fR (ulong)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Max arc size of ARC in bytes. If set to 0 then it will consume 1/2 of system
RAM. This value must be at least 67108864 (64 megabytes).
.sp
This value can be changed dynamically with some caveats. It cannot be set back
to 0 while running and reducing it below the current ARC size will not cause
the ARC to shrink without memory pressure to induce shrinking.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Update arc_memory_throttle() to check pageout This brings the behavior of arc_memory_throttle() back in sync with illumos. The updated memory throttling policy roughly goes like this: * Never throttle if more than 10% of memory is free. This threshold is configurable with the zfs_arc_lotsfree_percent module option. * Minimize any throttling of kswapd even when free memory is below the set threshold. Allow it to write out pages as quickly as possible to help alleviate the memory pressure. * Delay all other threads when free memory is below the set threshold in order to avoid compounding the memory pressure. Buffers will be evicted from the ARC to reduce the issue. The Linux specific zfs_arc_memory_throttle_disable module option has been removed in favor of the existing zfs_arc_lotsfree_percent tuning. Setting zfs_arc_lotsfree_percent=0 will have the same effect as zfs_arc_memory_throttle_disable and it was therefore redundant. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #3637
2015-07-28 21:30:00 +03:00
Default value: \fB0\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.RE
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 23:15:10 +03:00
.sp
.ne 2
.na
\fBzfs_arc_meta_adjust_restarts\fR (ulong)
.ad
.RS 12n
The number of restart passes to make while scanning the ARC attempting
the free buffers in order to stay below the \fBzfs_arc_meta_limit\fR.
This value should not need to be tuned but is available to facilitate
performance analysis.
.sp
Default value: \fB4096\fR.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
.ne 2
.na
\fBzfs_arc_meta_limit\fR (ulong)
.ad
.RS 12n
Restructure per-filesystem reclaim Originally when the ARC prune callback was introduced the idea was to register a single callback for the ZPL. The ARC could invoke this call back if it needed the ZPL to drop dentries, inodes, or other cache objects which might be pinning buffers in the ARC. The ZPL would iterate over all ZFS super blocks and perform the reclaim. For the most part this design has worked well but due to limitations in 2.6.35 and earlier kernels there were some problems. This patch is designed to address those issues. 1) iterate_supers_type() is not provided by all kernels which makes it impossible to safely iterate over all zpl_fs_type filesystems in a single callback. The most straight forward and portable way to resolve this is to register a callback per-filesystem during mount. The arc_*_prune_callback() functions have always supported multiple callbacks so this is functionally a very small change. 2) Commit 050d22b removed the non-portable shrink_dcache_memory() and shrink_icache_memory() functions and didn't replace them with equivalent functionality. This meant that for Linux 3.1 and older kernels the ARC had no mechanism to drop dentries and inodes from the caches if needed. This patch adds that missing functionality by calling shrink_dcache_parent() to release dentries which may be pinning inodes. This will result in all unused cache entries being dropped which is a bit heavy handed but it's the only interface available for old kernels. 3) A zpl_drop_inode() callback is registered for kernels older than 2.6.35 which do not support the .evict_inode callback. This ensures that when the last reference on an inode is dropped it is immediately removed from the cache. If this isn't done than inode can end up on the global unused LRU with no mechanism available to ZFS to drop them. Since the ARC buffers are not dropped the hottest inodes can still be recreated without performing disk IO. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Pavel Snajdr <snajpa@snajpa.net> Issue #3160
2015-03-18 01:07:47 +03:00
The maximum allowed size in bytes that meta data buffers are allowed to
consume in the ARC. When this limit is reached meta data buffers will
be reclaimed even if the overall arc_c_max has not been reached. This
Add zfs_arc_meta_limit_percent tunable ARC will evict meta buffers that exceed the arc_meta_limit. Before a further investigating on whether we should take special protection on meta buffers, this tunable make arc_meta_limit adjustable for different workloads. People can set zfs_arc_meta_limit_percent to any value while insmod zfs.ko, so some range check is added to guarantee a suitable arc_meta_limit. Suggested by Tim Chase, zfs_arc_dnode_limit is changed to a percent-style tunable as well. Signed-off-by: GeLiXin <ge.lixin@zte.com.cn> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4957
2016-08-11 06:15:37 +03:00
value defaults to 0 which indicates that a percent which is based on
\fBzfs_arc_meta_limit_percent\fR of the ARC may be used for meta data.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
This value my be changed dynamically except that it cannot be set back to 0
Add zfs_arc_meta_limit_percent tunable ARC will evict meta buffers that exceed the arc_meta_limit. Before a further investigating on whether we should take special protection on meta buffers, this tunable make arc_meta_limit adjustable for different workloads. People can set zfs_arc_meta_limit_percent to any value while insmod zfs.ko, so some range check is added to guarantee a suitable arc_meta_limit. Suggested by Tim Chase, zfs_arc_dnode_limit is changed to a percent-style tunable as well. Signed-off-by: GeLiXin <ge.lixin@zte.com.cn> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4957
2016-08-11 06:15:37 +03:00
for a specific percent of the ARC; it must be set to an explicit value.
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
.sp
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
Default value: \fB0\fR.
.RE
Add zfs_arc_meta_limit_percent tunable ARC will evict meta buffers that exceed the arc_meta_limit. Before a further investigating on whether we should take special protection on meta buffers, this tunable make arc_meta_limit adjustable for different workloads. People can set zfs_arc_meta_limit_percent to any value while insmod zfs.ko, so some range check is added to guarantee a suitable arc_meta_limit. Suggested by Tim Chase, zfs_arc_dnode_limit is changed to a percent-style tunable as well. Signed-off-by: GeLiXin <ge.lixin@zte.com.cn> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4957
2016-08-11 06:15:37 +03:00
.sp
.ne 2
.na
\fBzfs_arc_meta_limit_percent\fR (ulong)
.ad
.RS 12n
Percentage of ARC buffers that can be used for meta data.
See also \fBzfs_arc_meta_limit\fR which serves a similar purpose but has a
higher priority if set to nonzero value.
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 22:51:11 +03:00
Default value: \fB75\fR%.
Add zfs_arc_meta_limit_percent tunable ARC will evict meta buffers that exceed the arc_meta_limit. Before a further investigating on whether we should take special protection on meta buffers, this tunable make arc_meta_limit adjustable for different workloads. People can set zfs_arc_meta_limit_percent to any value while insmod zfs.ko, so some range check is added to guarantee a suitable arc_meta_limit. Suggested by Tim Chase, zfs_arc_dnode_limit is changed to a percent-style tunable as well. Signed-off-by: GeLiXin <ge.lixin@zte.com.cn> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4957
2016-08-11 06:15:37 +03:00
.RE
Illumos 5497 - lock contention on arcs_mtx Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Richard Elling <richard.elling@richardelling.com> Approved by: Dan McDonald <danmcd@omniti.com> Porting notes and other significant code changes: The illumos 5368 patch (ARC should cache more metadata), which was never picked up by ZoL, is mostly reverted by this patch. Since ZoL relies on the kernel asynchronously calling the shrinker to actually reap memory, the shrinker wakes up arc_reclaim_waiters_cv every time it runs. The arc_adapt_thread() function no longer calls arc_do_user_evicts() since the newly-added arc_user_evicts_thread() calls it periodically. Notable conflicting ZoL commits which conflicted with this patch or whose effects are either duplicated or un-done by this patch: 302f753 - Integrate ARC more tightly with Linux 39e055c - Adjust arc_p based on "bytes" in arc_shrink f521ce1 - Allow "arc_p" to drop to zero or grow to "arc_c" 77765b5 - Remove "arc_meta_used" from arc_adjust calculation 94520ca - Prune metadata from ghost lists in arc_adjust_meta Trace support for multilist_insert() and multilist_remove() has been added and produces the following output: fio-12498 [077] .... 112936.448324: zfs_multilist__insert: ml { offset 240 numsublists 80 sublistidx 63 } fio-12498 [077] .... 112936.448347: zfs_multilist__remove: ml { offset 240 numsublists 80 sublistidx 29 } The following arcstats have been removed: recycle_miss - Used by arcstat.py and arc_summary.py, both of which have been updated appropriately. l2_writes_hdr_miss The following arcstats have been added: evict_not_enough - Number of times arc_evict_state() was unable to evict enough buffers to reach its target amount. evict_l2_skip - Number of times arc_evict_hdr() skipped eviction because it was being written to the l2arc. l2_writes_lock_retry - Replaces l2_writes_hdr_miss. Number of times l2arc_write_done() failed to acquire hash_lock (and re-tries). arc_meta_min - Shows the value of the zfs_arc_meta_min module parameter (see below). The "index" column of the "dbuf" kstat has been removed since it doesn't have a direct analog in the new multilist scheme. Additional multilist- related stats could be added in the future but would likely require extensions to the mulilist API. The following module parameters have been added: zfs_arc_evict_batch_limit - Number of ARC headers to free per sub-list before moving on to the next sub-list. zfs_arc_meta_min - Enforce a floor on the amount of metadata in the ARC. zfs_arc_num_sublists_per_state - Number of multilist sub-lists per ARC state. zfs_arc_overflow_shift - Controls amount by which the ARC must exceed the target size to be considered "overflowing". Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov
2015-01-13 06:52:19 +03:00
.sp
.ne 2
.na
\fBzfs_arc_meta_min\fR (ulong)
.ad
.RS 12n
The minimum allowed size in bytes that meta data buffers may consume in
the ARC. This value defaults to 0 which disables a floor on the amount
of the ARC devoted meta data.
.sp
Default value: \fB0\fR.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
.ne 2
.na
\fBzfs_arc_meta_prune\fR (int)
.ad
.RS 12n
Restructure per-filesystem reclaim Originally when the ARC prune callback was introduced the idea was to register a single callback for the ZPL. The ARC could invoke this call back if it needed the ZPL to drop dentries, inodes, or other cache objects which might be pinning buffers in the ARC. The ZPL would iterate over all ZFS super blocks and perform the reclaim. For the most part this design has worked well but due to limitations in 2.6.35 and earlier kernels there were some problems. This patch is designed to address those issues. 1) iterate_supers_type() is not provided by all kernels which makes it impossible to safely iterate over all zpl_fs_type filesystems in a single callback. The most straight forward and portable way to resolve this is to register a callback per-filesystem during mount. The arc_*_prune_callback() functions have always supported multiple callbacks so this is functionally a very small change. 2) Commit 050d22b removed the non-portable shrink_dcache_memory() and shrink_icache_memory() functions and didn't replace them with equivalent functionality. This meant that for Linux 3.1 and older kernels the ARC had no mechanism to drop dentries and inodes from the caches if needed. This patch adds that missing functionality by calling shrink_dcache_parent() to release dentries which may be pinning inodes. This will result in all unused cache entries being dropped which is a bit heavy handed but it's the only interface available for old kernels. 3) A zpl_drop_inode() callback is registered for kernels older than 2.6.35 which do not support the .evict_inode callback. This ensures that when the last reference on an inode is dropped it is immediately removed from the cache. If this isn't done than inode can end up on the global unused LRU with no mechanism available to ZFS to drop them. Since the ARC buffers are not dropped the hottest inodes can still be recreated without performing disk IO. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Pavel Snajdr <snajpa@snajpa.net> Issue #3160
2015-03-18 01:07:47 +03:00
The number of dentries and inodes to be scanned looking for entries
which can be dropped. This may be required when the ARC reaches the
\fBzfs_arc_meta_limit\fR because dentries and inodes can pin buffers
in the ARC. Increasing this value will cause to dentry and inode caches
to be pruned more aggressively. Setting this value to 0 will disable
pruning the inode and dentry caches.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Restructure per-filesystem reclaim Originally when the ARC prune callback was introduced the idea was to register a single callback for the ZPL. The ARC could invoke this call back if it needed the ZPL to drop dentries, inodes, or other cache objects which might be pinning buffers in the ARC. The ZPL would iterate over all ZFS super blocks and perform the reclaim. For the most part this design has worked well but due to limitations in 2.6.35 and earlier kernels there were some problems. This patch is designed to address those issues. 1) iterate_supers_type() is not provided by all kernels which makes it impossible to safely iterate over all zpl_fs_type filesystems in a single callback. The most straight forward and portable way to resolve this is to register a callback per-filesystem during mount. The arc_*_prune_callback() functions have always supported multiple callbacks so this is functionally a very small change. 2) Commit 050d22b removed the non-portable shrink_dcache_memory() and shrink_icache_memory() functions and didn't replace them with equivalent functionality. This meant that for Linux 3.1 and older kernels the ARC had no mechanism to drop dentries and inodes from the caches if needed. This patch adds that missing functionality by calling shrink_dcache_parent() to release dentries which may be pinning inodes. This will result in all unused cache entries being dropped which is a bit heavy handed but it's the only interface available for old kernels. 3) A zpl_drop_inode() callback is registered for kernels older than 2.6.35 which do not support the .evict_inode callback. This ensures that when the last reference on an inode is dropped it is immediately removed from the cache. If this isn't done than inode can end up on the global unused LRU with no mechanism available to ZFS to drop them. Since the ARC buffers are not dropped the hottest inodes can still be recreated without performing disk IO. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Pavel Snajdr <snajpa@snajpa.net> Issue #3160
2015-03-18 01:07:47 +03:00
Default value: \fB10,000\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.RE
Fix arc_adjust_meta() behavior The goal of this function is to evict enough meta data buffers from the ARC in order to enforce the arc_meta_limit. Achieving this is slightly more complicated than it appears because it is common for data buffers to have holds on meta data buffers. In addition, dnode meta data buffers will be held by the dnodes in the block preventing them from being freed. This means we can't simply traverse the ARC and expect to always find enough unheld meta data buffer to release. Therefore, this function has been updated to make alternating passes over the ARC releasing data buffers and then newly unheld meta data buffers. This ensures forward progress is maintained and arc_meta_used will decrease. Normally this is sufficient, but if required the ARC will call the registered prune callbacks causing dentry and inodes to be dropped from the VFS cache. This will make dnode meta data buffers available for reclaim. The number of total restarts in limited by zfs_arc_meta_adjust_restarts to prevent spinning in the rare case where all meta data is pinned. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Pavel Snajdr <snajpa@snajpa.net> Issue #3160
2015-03-18 01:08:22 +03:00
.sp
.ne 2
.na
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 23:15:10 +03:00
\fBzfs_arc_meta_strategy\fR (int)
Fix arc_adjust_meta() behavior The goal of this function is to evict enough meta data buffers from the ARC in order to enforce the arc_meta_limit. Achieving this is slightly more complicated than it appears because it is common for data buffers to have holds on meta data buffers. In addition, dnode meta data buffers will be held by the dnodes in the block preventing them from being freed. This means we can't simply traverse the ARC and expect to always find enough unheld meta data buffer to release. Therefore, this function has been updated to make alternating passes over the ARC releasing data buffers and then newly unheld meta data buffers. This ensures forward progress is maintained and arc_meta_used will decrease. Normally this is sufficient, but if required the ARC will call the registered prune callbacks causing dentry and inodes to be dropped from the VFS cache. This will make dnode meta data buffers available for reclaim. The number of total restarts in limited by zfs_arc_meta_adjust_restarts to prevent spinning in the rare case where all meta data is pinned. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Pavel Snajdr <snajpa@snajpa.net> Issue #3160
2015-03-18 01:08:22 +03:00
.ad
.RS 12n
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 23:15:10 +03:00
Define the strategy for ARC meta data buffer eviction (meta reclaim strategy).
A value of 0 (META_ONLY) will evict only the ARC meta data buffers.
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 04:27:01 +03:00
A value of 1 (BALANCED) indicates that additional data buffers may be evicted if
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 23:15:10 +03:00
that is required to in order to evict the required number of meta data buffers.
Fix arc_adjust_meta() behavior The goal of this function is to evict enough meta data buffers from the ARC in order to enforce the arc_meta_limit. Achieving this is slightly more complicated than it appears because it is common for data buffers to have holds on meta data buffers. In addition, dnode meta data buffers will be held by the dnodes in the block preventing them from being freed. This means we can't simply traverse the ARC and expect to always find enough unheld meta data buffer to release. Therefore, this function has been updated to make alternating passes over the ARC releasing data buffers and then newly unheld meta data buffers. This ensures forward progress is maintained and arc_meta_used will decrease. Normally this is sufficient, but if required the ARC will call the registered prune callbacks causing dentry and inodes to be dropped from the VFS cache. This will make dnode meta data buffers available for reclaim. The number of total restarts in limited by zfs_arc_meta_adjust_restarts to prevent spinning in the rare case where all meta data is pinned. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Pavel Snajdr <snajpa@snajpa.net> Issue #3160
2015-03-18 01:08:22 +03:00
.sp
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 23:15:10 +03:00
Default value: \fB1\fR.
Fix arc_adjust_meta() behavior The goal of this function is to evict enough meta data buffers from the ARC in order to enforce the arc_meta_limit. Achieving this is slightly more complicated than it appears because it is common for data buffers to have holds on meta data buffers. In addition, dnode meta data buffers will be held by the dnodes in the block preventing them from being freed. This means we can't simply traverse the ARC and expect to always find enough unheld meta data buffer to release. Therefore, this function has been updated to make alternating passes over the ARC releasing data buffers and then newly unheld meta data buffers. This ensures forward progress is maintained and arc_meta_used will decrease. Normally this is sufficient, but if required the ARC will call the registered prune callbacks causing dentry and inodes to be dropped from the VFS cache. This will make dnode meta data buffers available for reclaim. The number of total restarts in limited by zfs_arc_meta_adjust_restarts to prevent spinning in the rare case where all meta data is pinned. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Pavel Snajdr <snajpa@snajpa.net> Issue #3160
2015-03-18 01:08:22 +03:00
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
.ne 2
.na
\fBzfs_arc_min\fR (ulong)
.ad
.RS 12n
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 23:15:10 +03:00
Min arc size of ARC in bytes. If set to 0 then arc_c_min will default to
consuming the larger of 32M or 1/32 of total system memory.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 23:15:10 +03:00
Default value: \fB0\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.RE
.sp
.ne 2
.na
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 04:27:01 +03:00
\fBzfs_arc_min_prefetch_ms\fR (int)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.ad
.RS 12n
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 04:27:01 +03:00
Minimum time prefetched blocks are locked in the ARC, specified in ms.
Adjust ARC prefetch tunables to match docs Currently, the ARC exposes 2 tunables (zfs_arc_min_prefetch_ms and zfs_arc_min_prescient_prefetch_ms) which are documented to be specified in milliseconds. However, the code actually uses the values as though they were in seconds. This patch adjusts the code to match the names and documentation of the tunables. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Reviewed by: George Melikov <mail@gmelikov.ru> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #7126
2018-02-06 03:57:53 +03:00
A value of \fB0\fR will default to 1000 ms.
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 04:27:01 +03:00
.sp
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
\fBzfs_arc_min_prescient_prefetch_ms\fR (int)
.ad
.RS 12n
Minimum time "prescient prefetched" blocks are locked in the ARC, specified
in ms. These blocks are meant to be prefetched fairly aggresively ahead of
Adjust ARC prefetch tunables to match docs Currently, the ARC exposes 2 tunables (zfs_arc_min_prefetch_ms and zfs_arc_min_prescient_prefetch_ms) which are documented to be specified in milliseconds. However, the code actually uses the values as though they were in seconds. This patch adjusts the code to match the names and documentation of the tunables. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Reviewed by: George Melikov <mail@gmelikov.ru> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #7126
2018-02-06 03:57:53 +03:00
the code that may use them. A value of \fB0\fR will default to 6000 ms.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Default value: \fB0\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.RE
OpenZFS 9075 - Improve ZFS pool import/load process and corrupted pool recovery Some work has been done lately to improve the debugability of the ZFS pool load (and import) process. This includes: 7638 Refactor spa_load_impl into several functions 8961 SPA load/import should tell us why it failed 7277 zdb should be able to print zfs_dbgmsg's To iterate on top of that, there's a few changes that were made to make the import process more resilient and crash free. One of the first tasks during the pool load process is to parse a config provided from userland that describes what devices the pool is composed of. A vdev tree is generated from that config, and then all the vdevs are opened. The Meta Object Set (MOS) of the pool is accessed, and several metadata objects that are necessary to load the pool are read. The exact configuration of the pool is also stored inside the MOS. Since the configuration provided from userland is external and might not accurately describe the vdev tree of the pool at the txg that is being loaded, it cannot be relied upon to safely operate the pool. For that reason, the configuration in the MOS is read early on. In the past, the two configurations were compared together and if there was a mismatch then the load process was aborted and an error was returned. The latter was a good way to ensure a pool does not get corrupted, however it made the pool load process needlessly fragile in cases where the vdev configuration changed or the userland configuration was outdated. Since the MOS is stored in 3 copies, the configuration provided by userland doesn't have to be perfect in order to read its contents. Hence, a new approach has been adopted: The pool is first opened with the untrusted userland configuration just so that the real configuration can be read from the MOS. The trusted MOS configuration is then used to generate a new vdev tree and the pool is re-opened. When the pool is opened with an untrusted configuration, writes are disabled to avoid accidentally damaging it. During reads, some sanity checks are performed on block pointers to see if each DVA points to a known vdev; when the configuration is untrusted, instead of panicking the system if those checks fail we simply avoid issuing reads to the invalid DVAs. This new two-step pool load process now allows rewinding pools accross vdev tree changes such as device replacement, addition, etc. Loading a pool from an external config file in a clustering environment also becomes much safer now since the pool will import even if the config is outdated and didn't, for instance, register a recent device addition. With this code in place, it became relatively easy to implement a long-sought-after feature: the ability to import a pool with missing top level (i.e. non-redundant) devices. Note that since this almost guarantees some loss of data, this feature is for now restricted to a read-only import. Porting notes (ZTS): * Fix 'make dist' target in zpool_import * The maximum path length allowed by tar is 99 characters. Several of the new test cases exceeded this limit resulting in them not being included in the tarball. Shorten the names slightly. * Set/get tunables using accessor functions. * Get last synced txg via the "zfs_txg_history" mechanism. * Clear zinject handlers in cleanup for import_cache_device_replaced and import_rewind_device_replaced in order that the zpool can be exported if there is an error. * Increase FILESIZE to 8G in zfs-test.sh to allow for a larger ext4 file system to be created on ZFS_DISK2. Also, there's no need to partition ZFS_DISK2 at all. The partitioning had already been disabled for multipath devices. Among other things, the partitioning steals some space from the ext4 file system, makes it difficult to accurately calculate the paramters to parted and can make some of the tests fail. * Increase FS_SIZE and FILE_SIZE in the zpool_import test configuration now that FILESIZE is larger. * Write more data in order that device evacuation take lonnger in a couple tests. * Use mkdir -p to avoid errors when the directory already exists. * Remove use of sudo in import_rewind_config_changed. Authored by: Pavel Zakharov <pavel.zakharov@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Andrew Stormont <andyjstormont@gmail.com> Approved by: Hans Rosenfeld <rosenfeld@grumpf.hope-2000.org> Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Tim Chase <tim@chase2k.com> OpenZFS-issue: https://illumos.org/issues/9075 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/619c0123 Closes #7459
2016-07-22 17:39:36 +03:00
.sp
.ne 2
.na
\fBzfs_max_missing_tvds\fR (int)
.ad
.RS 12n
Number of missing top-level vdevs which will be allowed during
pool import (only in read-only mode).
.sp
Default value: \fB0\fR
.RE
Illumos 5497 - lock contention on arcs_mtx Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Richard Elling <richard.elling@richardelling.com> Approved by: Dan McDonald <danmcd@omniti.com> Porting notes and other significant code changes: The illumos 5368 patch (ARC should cache more metadata), which was never picked up by ZoL, is mostly reverted by this patch. Since ZoL relies on the kernel asynchronously calling the shrinker to actually reap memory, the shrinker wakes up arc_reclaim_waiters_cv every time it runs. The arc_adapt_thread() function no longer calls arc_do_user_evicts() since the newly-added arc_user_evicts_thread() calls it periodically. Notable conflicting ZoL commits which conflicted with this patch or whose effects are either duplicated or un-done by this patch: 302f753 - Integrate ARC more tightly with Linux 39e055c - Adjust arc_p based on "bytes" in arc_shrink f521ce1 - Allow "arc_p" to drop to zero or grow to "arc_c" 77765b5 - Remove "arc_meta_used" from arc_adjust calculation 94520ca - Prune metadata from ghost lists in arc_adjust_meta Trace support for multilist_insert() and multilist_remove() has been added and produces the following output: fio-12498 [077] .... 112936.448324: zfs_multilist__insert: ml { offset 240 numsublists 80 sublistidx 63 } fio-12498 [077] .... 112936.448347: zfs_multilist__remove: ml { offset 240 numsublists 80 sublistidx 29 } The following arcstats have been removed: recycle_miss - Used by arcstat.py and arc_summary.py, both of which have been updated appropriately. l2_writes_hdr_miss The following arcstats have been added: evict_not_enough - Number of times arc_evict_state() was unable to evict enough buffers to reach its target amount. evict_l2_skip - Number of times arc_evict_hdr() skipped eviction because it was being written to the l2arc. l2_writes_lock_retry - Replaces l2_writes_hdr_miss. Number of times l2arc_write_done() failed to acquire hash_lock (and re-tries). arc_meta_min - Shows the value of the zfs_arc_meta_min module parameter (see below). The "index" column of the "dbuf" kstat has been removed since it doesn't have a direct analog in the new multilist scheme. Additional multilist- related stats could be added in the future but would likely require extensions to the mulilist API. The following module parameters have been added: zfs_arc_evict_batch_limit - Number of ARC headers to free per sub-list before moving on to the next sub-list. zfs_arc_meta_min - Enforce a floor on the amount of metadata in the ARC. zfs_arc_num_sublists_per_state - Number of multilist sub-lists per ARC state. zfs_arc_overflow_shift - Controls amount by which the ARC must exceed the target size to be considered "overflowing". Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov
2015-01-13 06:52:19 +03:00
.sp
.ne 2
.na
zfs_arc_num_sublists_per_state should be common to all multilists The global tunable zfs_arc_num_sublists_per_state is used by the ARC and the dbuf cache, and other users are planned. We should change this tunable to be common to all multilists. This tuning may be overridden on a per-multilist basis. Reviewed-by: Pavel Zakharov <pavel.zakharov@delphix.com> Reviewed-by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed-by: Tony Hutter <hutter2@llnl.gov> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> Closes #5764
2017-02-16 02:49:33 +03:00
\fBzfs_multilist_num_sublists\fR (int)
Illumos 5497 - lock contention on arcs_mtx Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Richard Elling <richard.elling@richardelling.com> Approved by: Dan McDonald <danmcd@omniti.com> Porting notes and other significant code changes: The illumos 5368 patch (ARC should cache more metadata), which was never picked up by ZoL, is mostly reverted by this patch. Since ZoL relies on the kernel asynchronously calling the shrinker to actually reap memory, the shrinker wakes up arc_reclaim_waiters_cv every time it runs. The arc_adapt_thread() function no longer calls arc_do_user_evicts() since the newly-added arc_user_evicts_thread() calls it periodically. Notable conflicting ZoL commits which conflicted with this patch or whose effects are either duplicated or un-done by this patch: 302f753 - Integrate ARC more tightly with Linux 39e055c - Adjust arc_p based on "bytes" in arc_shrink f521ce1 - Allow "arc_p" to drop to zero or grow to "arc_c" 77765b5 - Remove "arc_meta_used" from arc_adjust calculation 94520ca - Prune metadata from ghost lists in arc_adjust_meta Trace support for multilist_insert() and multilist_remove() has been added and produces the following output: fio-12498 [077] .... 112936.448324: zfs_multilist__insert: ml { offset 240 numsublists 80 sublistidx 63 } fio-12498 [077] .... 112936.448347: zfs_multilist__remove: ml { offset 240 numsublists 80 sublistidx 29 } The following arcstats have been removed: recycle_miss - Used by arcstat.py and arc_summary.py, both of which have been updated appropriately. l2_writes_hdr_miss The following arcstats have been added: evict_not_enough - Number of times arc_evict_state() was unable to evict enough buffers to reach its target amount. evict_l2_skip - Number of times arc_evict_hdr() skipped eviction because it was being written to the l2arc. l2_writes_lock_retry - Replaces l2_writes_hdr_miss. Number of times l2arc_write_done() failed to acquire hash_lock (and re-tries). arc_meta_min - Shows the value of the zfs_arc_meta_min module parameter (see below). The "index" column of the "dbuf" kstat has been removed since it doesn't have a direct analog in the new multilist scheme. Additional multilist- related stats could be added in the future but would likely require extensions to the mulilist API. The following module parameters have been added: zfs_arc_evict_batch_limit - Number of ARC headers to free per sub-list before moving on to the next sub-list. zfs_arc_meta_min - Enforce a floor on the amount of metadata in the ARC. zfs_arc_num_sublists_per_state - Number of multilist sub-lists per ARC state. zfs_arc_overflow_shift - Controls amount by which the ARC must exceed the target size to be considered "overflowing". Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov
2015-01-13 06:52:19 +03:00
.ad
.RS 12n
To allow more fine-grained locking, each ARC state contains a series
of lists for both data and meta data objects. Locking is performed at
the level of these "sub-lists". This parameters controls the number of
zfs_arc_num_sublists_per_state should be common to all multilists The global tunable zfs_arc_num_sublists_per_state is used by the ARC and the dbuf cache, and other users are planned. We should change this tunable to be common to all multilists. This tuning may be overridden on a per-multilist basis. Reviewed-by: Pavel Zakharov <pavel.zakharov@delphix.com> Reviewed-by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed-by: Tony Hutter <hutter2@llnl.gov> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> Closes #5764
2017-02-16 02:49:33 +03:00
sub-lists per ARC state, and also applies to other uses of the
multilist data structure.
Illumos 5497 - lock contention on arcs_mtx Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Richard Elling <richard.elling@richardelling.com> Approved by: Dan McDonald <danmcd@omniti.com> Porting notes and other significant code changes: The illumos 5368 patch (ARC should cache more metadata), which was never picked up by ZoL, is mostly reverted by this patch. Since ZoL relies on the kernel asynchronously calling the shrinker to actually reap memory, the shrinker wakes up arc_reclaim_waiters_cv every time it runs. The arc_adapt_thread() function no longer calls arc_do_user_evicts() since the newly-added arc_user_evicts_thread() calls it periodically. Notable conflicting ZoL commits which conflicted with this patch or whose effects are either duplicated or un-done by this patch: 302f753 - Integrate ARC more tightly with Linux 39e055c - Adjust arc_p based on "bytes" in arc_shrink f521ce1 - Allow "arc_p" to drop to zero or grow to "arc_c" 77765b5 - Remove "arc_meta_used" from arc_adjust calculation 94520ca - Prune metadata from ghost lists in arc_adjust_meta Trace support for multilist_insert() and multilist_remove() has been added and produces the following output: fio-12498 [077] .... 112936.448324: zfs_multilist__insert: ml { offset 240 numsublists 80 sublistidx 63 } fio-12498 [077] .... 112936.448347: zfs_multilist__remove: ml { offset 240 numsublists 80 sublistidx 29 } The following arcstats have been removed: recycle_miss - Used by arcstat.py and arc_summary.py, both of which have been updated appropriately. l2_writes_hdr_miss The following arcstats have been added: evict_not_enough - Number of times arc_evict_state() was unable to evict enough buffers to reach its target amount. evict_l2_skip - Number of times arc_evict_hdr() skipped eviction because it was being written to the l2arc. l2_writes_lock_retry - Replaces l2_writes_hdr_miss. Number of times l2arc_write_done() failed to acquire hash_lock (and re-tries). arc_meta_min - Shows the value of the zfs_arc_meta_min module parameter (see below). The "index" column of the "dbuf" kstat has been removed since it doesn't have a direct analog in the new multilist scheme. Additional multilist- related stats could be added in the future but would likely require extensions to the mulilist API. The following module parameters have been added: zfs_arc_evict_batch_limit - Number of ARC headers to free per sub-list before moving on to the next sub-list. zfs_arc_meta_min - Enforce a floor on the amount of metadata in the ARC. zfs_arc_num_sublists_per_state - Number of multilist sub-lists per ARC state. zfs_arc_overflow_shift - Controls amount by which the ARC must exceed the target size to be considered "overflowing". Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov
2015-01-13 06:52:19 +03:00
.sp
zfs_arc_num_sublists_per_state should be common to all multilists The global tunable zfs_arc_num_sublists_per_state is used by the ARC and the dbuf cache, and other users are planned. We should change this tunable to be common to all multilists. This tuning may be overridden on a per-multilist basis. Reviewed-by: Pavel Zakharov <pavel.zakharov@delphix.com> Reviewed-by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed-by: Tony Hutter <hutter2@llnl.gov> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> Closes #5764
2017-02-16 02:49:33 +03:00
Default value: \fB4\fR or the number of online CPUs, whichever is greater
Illumos 5497 - lock contention on arcs_mtx Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Richard Elling <richard.elling@richardelling.com> Approved by: Dan McDonald <danmcd@omniti.com> Porting notes and other significant code changes: The illumos 5368 patch (ARC should cache more metadata), which was never picked up by ZoL, is mostly reverted by this patch. Since ZoL relies on the kernel asynchronously calling the shrinker to actually reap memory, the shrinker wakes up arc_reclaim_waiters_cv every time it runs. The arc_adapt_thread() function no longer calls arc_do_user_evicts() since the newly-added arc_user_evicts_thread() calls it periodically. Notable conflicting ZoL commits which conflicted with this patch or whose effects are either duplicated or un-done by this patch: 302f753 - Integrate ARC more tightly with Linux 39e055c - Adjust arc_p based on "bytes" in arc_shrink f521ce1 - Allow "arc_p" to drop to zero or grow to "arc_c" 77765b5 - Remove "arc_meta_used" from arc_adjust calculation 94520ca - Prune metadata from ghost lists in arc_adjust_meta Trace support for multilist_insert() and multilist_remove() has been added and produces the following output: fio-12498 [077] .... 112936.448324: zfs_multilist__insert: ml { offset 240 numsublists 80 sublistidx 63 } fio-12498 [077] .... 112936.448347: zfs_multilist__remove: ml { offset 240 numsublists 80 sublistidx 29 } The following arcstats have been removed: recycle_miss - Used by arcstat.py and arc_summary.py, both of which have been updated appropriately. l2_writes_hdr_miss The following arcstats have been added: evict_not_enough - Number of times arc_evict_state() was unable to evict enough buffers to reach its target amount. evict_l2_skip - Number of times arc_evict_hdr() skipped eviction because it was being written to the l2arc. l2_writes_lock_retry - Replaces l2_writes_hdr_miss. Number of times l2arc_write_done() failed to acquire hash_lock (and re-tries). arc_meta_min - Shows the value of the zfs_arc_meta_min module parameter (see below). The "index" column of the "dbuf" kstat has been removed since it doesn't have a direct analog in the new multilist scheme. Additional multilist- related stats could be added in the future but would likely require extensions to the mulilist API. The following module parameters have been added: zfs_arc_evict_batch_limit - Number of ARC headers to free per sub-list before moving on to the next sub-list. zfs_arc_meta_min - Enforce a floor on the amount of metadata in the ARC. zfs_arc_num_sublists_per_state - Number of multilist sub-lists per ARC state. zfs_arc_overflow_shift - Controls amount by which the ARC must exceed the target size to be considered "overflowing". Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov
2015-01-13 06:52:19 +03:00
.RE
.sp
.ne 2
.na
\fBzfs_arc_overflow_shift\fR (int)
.ad
.RS 12n
The ARC size is considered to be overflowing if it exceeds the current
ARC target size (arc_c) by a threshold determined by this parameter.
The threshold is calculated as a fraction of arc_c using the formula
"arc_c >> \fBzfs_arc_overflow_shift\fR".
The default value of 8 causes the ARC to be considered to be overflowing
if it exceeds the target size by 1/256th (0.3%) of the target size.
When the ARC is overflowing, new buffer allocations are stalled until
the reclaim thread catches up and the overflow condition no longer exists.
.sp
Default value: \fB8\fR.
.RE
Reinstate zfs_arc_p_min_shift Commit f521ce1 removed the minimum value for "arc_p" allowing it to drop to zero or grow to "arc_c". This was done to improve specific workload which constantly dirties new "metadata" but also frequently touches a "small" amount of mfu data (e.g. mkdir's). This change may still be desirable but it needs to be re-investigated. in the context of the recent ARC changes from upstream. Therefore this code is being restored to facilitate benchmarking. By setting "zfs_arc_p_min_shift=64" we easily compare the performance. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #3533
2015-06-27 01:59:23 +03:00
.sp
.ne 2
.na
\fBzfs_arc_p_min_shift\fR (int)
.ad
.RS 12n
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 23:15:10 +03:00
If set to a non zero value, this will update arc_p_min_shift (default 4)
with the new value.
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 04:27:01 +03:00
arc_p_min_shift is used to shift of arc_c for calculating both min and max
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 23:15:10 +03:00
max arc_p
Reinstate zfs_arc_p_min_shift Commit f521ce1 removed the minimum value for "arc_p" allowing it to drop to zero or grow to "arc_c". This was done to improve specific workload which constantly dirties new "metadata" but also frequently touches a "small" amount of mfu data (e.g. mkdir's). This change may still be desirable but it needs to be re-investigated. in the context of the recent ARC changes from upstream. Therefore this code is being restored to facilitate benchmarking. By setting "zfs_arc_p_min_shift=64" we easily compare the performance. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #3533
2015-06-27 01:59:23 +03:00
.sp
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 23:15:10 +03:00
Default value: \fB0\fR.
Reinstate zfs_arc_p_min_shift Commit f521ce1 removed the minimum value for "arc_p" allowing it to drop to zero or grow to "arc_c". This was done to improve specific workload which constantly dirties new "metadata" but also frequently touches a "small" amount of mfu data (e.g. mkdir's). This change may still be desirable but it needs to be re-investigated. in the context of the recent ARC changes from upstream. Therefore this code is being restored to facilitate benchmarking. By setting "zfs_arc_p_min_shift=64" we easily compare the performance. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #3533
2015-06-27 01:59:23 +03:00
.RE
Disable arc_p adapt dampener by default It's unclear why adjustments to arc_p need to be dampened as they are in arc_adjust. With that said, it's removal significantly improves the arc's ability to "warm up" to a given workload. Thus, I'm disabling by default until its usefulness is better understood. Signed-off-by: Prakash Surya <surya1@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #2110
2014-01-03 22:36:26 +04:00
.sp
.ne 2
.na
\fBzfs_arc_p_dampener_disable\fR (int)
.ad
.RS 12n
Disable arc_p adapt dampener
.sp
Use \fB1\fR for yes (default) and \fB0\fR to disable.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
.ne 2
.na
\fBzfs_arc_shrink_shift\fR (int)
.ad
.RS 12n
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 23:15:10 +03:00
If set to a non zero value, this will update arc_shrink_shift (default 7)
with the new value.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 23:15:10 +03:00
Default value: \fB0\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.RE
Allow scaling of arc in proportion to pagecache When multiple filesystems are in use, memory pressure causes arc_cache to collapse to a minimum. Allow arc_cache to maintain proportional size even when hit rates are disproportionate. We do this only via evictable size from the kernel shrinker, thus it's only in effect under memory pressure. AKAMAI: zfs: CR 3695072 Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed-by: Richard Yao <ryao@gentoo.org> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Debabrata Banerjee <dbanerje@akamai.com> Closes #6035
2017-03-16 04:34:56 +03:00
.sp
.ne 2
.na
\fBzfs_arc_pc_percent\fR (uint)
.ad
.RS 12n
Percent of pagecache to reclaim arc to
This tunable allows ZFS arc to play more nicely with the kernel's LRU
pagecache. It can guarantee that the arc size won't collapse under scanning
pressure on the pagecache, yet still allows arc to be reclaimed down to
zfs_arc_min if necessary. This value is specified as percent of pagecache
size (as measured by NR_FILE_PAGES) where that percent may exceed 100. This
only operates during memory pressure/reclaim.
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 22:51:11 +03:00
Default value: \fB0\fR% (disabled).
Allow scaling of arc in proportion to pagecache When multiple filesystems are in use, memory pressure causes arc_cache to collapse to a minimum. Allow arc_cache to maintain proportional size even when hit rates are disproportionate. We do this only via evictable size from the kernel shrinker, thus it's only in effect under memory pressure. AKAMAI: zfs: CR 3695072 Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed-by: Richard Yao <ryao@gentoo.org> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Debabrata Banerjee <dbanerje@akamai.com> Closes #6035
2017-03-16 04:34:56 +03:00
.RE
Update arc_available_memory() to check freemem While Linux doesn't provide detailed information about the state of the VM it does provide us total free pages. This information should be incorporated in to the arc_available_memory() calculation rather than solely relying on a signal from direct reclaim. Conceptually this brings arc_available_memory() back in sync with illumos. It is also desirable that the target amount of free memory be tunable on a system. While the default values are expected to work well for most workloads there may be cases where custom values are needed. The zfs_arc_sys_free module option was added for this purpose. zfs_arc_sys_free - The target number of bytes the ARC should leave as free memory on the system. This value can checked in /proc/spl/kstat/zfs/arcstats and setting this module option will override the default value. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #3637
2015-07-27 23:17:32 +03:00
.sp
.ne 2
.na
\fBzfs_arc_sys_free\fR (ulong)
.ad
.RS 12n
The target number of bytes the ARC should leave as free memory on the system.
Defaults to the larger of 1/64 of physical memory or 512K. Setting this
option to a non-zero value will override the default.
.sp
Default value: \fB0\fR.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
.ne 2
.na
\fBzfs_autoimport_disable\fR (int)
.ad
.RS 12n
Expand the description of scan-related and other parameters. Document that the scan-related parameters are, in fact, applicable only to scrub and/or resilver operations as appropriate. Expand a few of the prefetch-related descriptions. Add clarification to other module parameters. Signed-off-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2361
2014-06-04 16:23:31 +04:00
Disable pool import at module load by ignoring the cache file (typically \fB/etc/zfs/zpool.cache\fR).
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
align zfs_autoimport_disable manpage with reality The default was changed in #2820. Signed-off-by: cburroughs <chris.burroughs@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #3341
2015-04-24 21:03:26 +03:00
Use \fB1\fR for yes (default) and \fB0\fR for no.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.RE
Change checksum & IO delay ratelimit values Change checksum & IO delay ratelimit thresholds from 5/sec to 20/sec. This allows zed to actually trigger if a bunch of these events arrive in a short period of time (zed has a threshold of 10 events in 10 sec). Previously, if you had, say, 100 checksum errors in 1 sec, it would get ratelimited to 5/sec which wouldn't trigger zed to fault the drive. Also, convert the checksum and IO delay thresholds to module params for easy testing. Reviewed-by: loli10K <ezomori.nozomu@gmail.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Tony Hutter <hutter2@llnl.gov> Closes #7252
2018-03-05 04:34:51 +03:00
.sp
.ne 2
.na
\fBzfs_checksums_per_second\fR (int)
.ad
.RS 12n
Rate limit checksum events to this many per second. Note that this should
not be set below the zed thresholds (currently 10 checksums over 10 sec)
or else zed may not trigger any action.
.sp
Default value: 20
.RE
OpenZFS 8909 - 8585 can cause a use-after-free kernel panic Authored by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: John Kennedy <jwk404@gmail.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Brad Lewis <brad.lewis@delphix.com> Reviewed by: Igor Kozhukhov <igor@dilos.org> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Robert Mustacchi <rm@joyent.com> Ported-by: Prakash Surya <prakash.surya@delphix.com> PROBLEM ======= There's a race condition that exists if `zil_free_lwb` races with either `zil_commit_waiter_timeout` and/or `zil_lwb_flush_vdevs_done`. Here's an example panic due to this bug: > ::status debugging crash dump vmcore.0 (64-bit) from ip-10-110-205-40 operating system: 5.11 dlpx-5.2.2.0_2017-12-04-17-28-32b6ba51fb (i86pc) image uuid: 4af0edfb-e58e-6ed8-cafc-d3e9167c7513 panic message: BAD TRAP: type=e (#pf Page fault) rp=ffffff0010555970 addr=60 occurred in module "zfs" due to a NULL pointer dereference dump content: kernel pages only > $c zio_shrink+0x12() zil_lwb_write_issue+0x30d(ffffff03dcd15cc0, ffffff03e0730e20) zil_commit_waiter_timeout+0xa2(ffffff03dcd15cc0, ffffff03d97ffcf8) zil_commit_waiter+0xf3(ffffff03dcd15cc0, ffffff03d97ffcf8) zil_commit+0x80(ffffff03dcd15cc0, 9a9) zfs_write+0xc34(ffffff03dc38b140, ffffff0010555e60, 40, ffffff03e00fb758, 0) fop_write+0x5b(ffffff03dc38b140, ffffff0010555e60, 40, ffffff03e00fb758, 0) write+0x250(42, fffffd7ff4832000, 2000) sys_syscall+0x177() If there's an outstanding lwb that's in `zil_commit_waiter_timeout` waiting to timeout, waiting on it's waiter's CV, we must be sure not to call `zil_free_lwb`. If we end up calling `zil_free_lwb`, then that LWB may be freed and can result in a use-after-free situation where the stale lwb pointer stored in the `zil_commit_waiter_t` structure of the thread waiting on the waiter's CV is used. A similar situation can occur if an lwb is issued to disk, and thus in the `LWB_STATE_ISSUED` state, and `zil_free_lwb` is called while the disk is servicing that lwb. In this situation, the lwb will be freed by `zil_free_lwb`, which will result in a use-after-free situation when the lwb's zio completes, and `zil_lwb_flush_vdevs_done` is called. This race condition is prevented in `zil_close` by calling `zil_commit` before `zil_free_lwb` is called, which will ensure all outstanding (i.e. all lwb's in the `LWB_STATE_OPEN` and/or `LWB_STATE_ISSUED` states) reach the `LWB_STATE_DONE` state before the lwb's are freed (`zil_commit` will not return untill all the lwb's are `LWB_STATE_DONE`). Further, this race condition is prevented in `zil_sync` by only calling `zil_free_lwb` for lwb's that do not have their `lwb_buf` pointer set. All lwb's not in the `LWB_STATE_DONE` state will have a non-null value for this pointer; the pointer is only cleared in `zil_lwb_flush_vdevs_done`, at which point the lwb's state will be changed to `LWB_STATE_DONE`. This race *is* present in `zil_suspend`, leading to this bug. At first glance, it would appear as though this would not be true because `zil_suspend` will call `zil_commit`, just like `zil_close`, but the problem is that `zil_suspend` will set the zilog's `zl_suspend` field prior to calling `zil_commit`. Further, in `zil_commit`, if `zl_suspend` is set, `zil_commit` will take a special branch of logic and use `txg_wait_synced` instead of performing the normal `zil_commit` logic. This call to `txg_wait_synced` might be good enough for the data to reach disk safely before it returns, but it does not ensure that all outstanding lwb's reach the `LWB_STATE_DONE` state before it returns. This is because, if there's an lwb "stuck" in `zil_commit_waiter_timeout`, waiting for it's lwb to timeout, it will maintain a non-null value for it's `lwb_buf` field and thus `zil_sync` will not free that lwb. Thus, even though the lwb's data is already on disk, the lwb will be left lingering, waiting on the CV, and will eventually timeout and be issued to disk even though the write is unnecessary. So, after `zil_commit` is called from `zil_suspend`, we incorrectly assume that there are not outstanding lwb's, and proceed to free all lwb's found on the zilog's lwb list. As a result, we free the lwb that will later be used `zil_commit_waiter_timeout`. SOLUTION ======== The solution to this, is to ensure all outstanding lwb's complete before calling `zil_free_lwb` via `zil_destroy` in `zil_suspend`. This patch accomplishes this goal by forcing the normal `zil_commit` logic when called from `zil_sync`. Now, `zil_suspend` will call `zil_commit_impl` which will always use the normal logic of waiting/issuing lwb's to disk before it returns. As a result, any lwb's outstanding when `zil_commit_impl` is called will be guaranteed to reach the `LWB_STATE_DONE` state by the time it returns. Further, no new lwb's will be created via `zil_commit` since the zilog's `zl_suspend` flag will be set. This will force all new callers of `zil_commit` to use `txg_wait_synced` instead of creating and issuing new lwb's. Thus, all lwb's left on the zilog's lwb list when `zil_destroy` is called will be in the `LWB_STATE_DONE` state, and we'll avoid this race condition. OpenZFS-issue: https://www.illumos.org/issues/8909 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/ece62b6f8d Closes #6940
2017-12-07 22:26:32 +03:00
.sp
.ne 2
.na
\fBzfs_commit_timeout_pct\fR (int)
.ad
.RS 12n
This controls the amount of time that a ZIL block (lwb) will remain "open"
when it isn't "full", and it has a thread waiting for it to be committed to
stable storage. The timeout is scaled based on a percentage of the last lwb
latency to avoid significantly impacting the latency of each individual
transaction record (itx).
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 22:51:11 +03:00
Default value: \fB5\fR%.
OpenZFS 8909 - 8585 can cause a use-after-free kernel panic Authored by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: John Kennedy <jwk404@gmail.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Brad Lewis <brad.lewis@delphix.com> Reviewed by: Igor Kozhukhov <igor@dilos.org> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Robert Mustacchi <rm@joyent.com> Ported-by: Prakash Surya <prakash.surya@delphix.com> PROBLEM ======= There's a race condition that exists if `zil_free_lwb` races with either `zil_commit_waiter_timeout` and/or `zil_lwb_flush_vdevs_done`. Here's an example panic due to this bug: > ::status debugging crash dump vmcore.0 (64-bit) from ip-10-110-205-40 operating system: 5.11 dlpx-5.2.2.0_2017-12-04-17-28-32b6ba51fb (i86pc) image uuid: 4af0edfb-e58e-6ed8-cafc-d3e9167c7513 panic message: BAD TRAP: type=e (#pf Page fault) rp=ffffff0010555970 addr=60 occurred in module "zfs" due to a NULL pointer dereference dump content: kernel pages only > $c zio_shrink+0x12() zil_lwb_write_issue+0x30d(ffffff03dcd15cc0, ffffff03e0730e20) zil_commit_waiter_timeout+0xa2(ffffff03dcd15cc0, ffffff03d97ffcf8) zil_commit_waiter+0xf3(ffffff03dcd15cc0, ffffff03d97ffcf8) zil_commit+0x80(ffffff03dcd15cc0, 9a9) zfs_write+0xc34(ffffff03dc38b140, ffffff0010555e60, 40, ffffff03e00fb758, 0) fop_write+0x5b(ffffff03dc38b140, ffffff0010555e60, 40, ffffff03e00fb758, 0) write+0x250(42, fffffd7ff4832000, 2000) sys_syscall+0x177() If there's an outstanding lwb that's in `zil_commit_waiter_timeout` waiting to timeout, waiting on it's waiter's CV, we must be sure not to call `zil_free_lwb`. If we end up calling `zil_free_lwb`, then that LWB may be freed and can result in a use-after-free situation where the stale lwb pointer stored in the `zil_commit_waiter_t` structure of the thread waiting on the waiter's CV is used. A similar situation can occur if an lwb is issued to disk, and thus in the `LWB_STATE_ISSUED` state, and `zil_free_lwb` is called while the disk is servicing that lwb. In this situation, the lwb will be freed by `zil_free_lwb`, which will result in a use-after-free situation when the lwb's zio completes, and `zil_lwb_flush_vdevs_done` is called. This race condition is prevented in `zil_close` by calling `zil_commit` before `zil_free_lwb` is called, which will ensure all outstanding (i.e. all lwb's in the `LWB_STATE_OPEN` and/or `LWB_STATE_ISSUED` states) reach the `LWB_STATE_DONE` state before the lwb's are freed (`zil_commit` will not return untill all the lwb's are `LWB_STATE_DONE`). Further, this race condition is prevented in `zil_sync` by only calling `zil_free_lwb` for lwb's that do not have their `lwb_buf` pointer set. All lwb's not in the `LWB_STATE_DONE` state will have a non-null value for this pointer; the pointer is only cleared in `zil_lwb_flush_vdevs_done`, at which point the lwb's state will be changed to `LWB_STATE_DONE`. This race *is* present in `zil_suspend`, leading to this bug. At first glance, it would appear as though this would not be true because `zil_suspend` will call `zil_commit`, just like `zil_close`, but the problem is that `zil_suspend` will set the zilog's `zl_suspend` field prior to calling `zil_commit`. Further, in `zil_commit`, if `zl_suspend` is set, `zil_commit` will take a special branch of logic and use `txg_wait_synced` instead of performing the normal `zil_commit` logic. This call to `txg_wait_synced` might be good enough for the data to reach disk safely before it returns, but it does not ensure that all outstanding lwb's reach the `LWB_STATE_DONE` state before it returns. This is because, if there's an lwb "stuck" in `zil_commit_waiter_timeout`, waiting for it's lwb to timeout, it will maintain a non-null value for it's `lwb_buf` field and thus `zil_sync` will not free that lwb. Thus, even though the lwb's data is already on disk, the lwb will be left lingering, waiting on the CV, and will eventually timeout and be issued to disk even though the write is unnecessary. So, after `zil_commit` is called from `zil_suspend`, we incorrectly assume that there are not outstanding lwb's, and proceed to free all lwb's found on the zilog's lwb list. As a result, we free the lwb that will later be used `zil_commit_waiter_timeout`. SOLUTION ======== The solution to this, is to ensure all outstanding lwb's complete before calling `zil_free_lwb` via `zil_destroy` in `zil_suspend`. This patch accomplishes this goal by forcing the normal `zil_commit` logic when called from `zil_sync`. Now, `zil_suspend` will call `zil_commit_impl` which will always use the normal logic of waiting/issuing lwb's to disk before it returns. As a result, any lwb's outstanding when `zil_commit_impl` is called will be guaranteed to reach the `LWB_STATE_DONE` state by the time it returns. Further, no new lwb's will be created via `zil_commit` since the zilog's `zl_suspend` flag will be set. This will force all new callers of `zil_commit` to use `txg_wait_synced` instead of creating and issuing new lwb's. Thus, all lwb's left on the zilog's lwb list when `zil_destroy` is called will be in the `LWB_STATE_DONE` state, and we'll avoid this race condition. OpenZFS-issue: https://www.illumos.org/issues/8909 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/ece62b6f8d Closes #6940
2017-12-07 22:26:32 +03:00
.RE
OpenZFS 9486 - reduce memory used by device removal on fragmented pools Device removal allocates a new location for each allocated segment on the disk that's being removed. Each allocation results in one entry in the mapping table, which maps from old location + length to new location. When a fragmented disk is removed, this can result in a large number of mapping entries, and thus a large amount of memory consumed by the mapping table. In the worst real-world cases, we've seen around 1GB of RAM per 1TB of storage removed. We can improve on this situation by allocating larger segments, which span across both allocated and free regions of the device being removed. By including free regions in the allocation (and thus mapping), we reduce the number of mapping entries. For example, if we have a 4K allocation followed by 1K free and then 4K allocated, we would allocate 4+1+4 = 9KB, and then move the entire region (including allocated and free parts). In this case we used one mapping where previously we would have used two, but often the ratio is much higher (up to 20:1 in real-world use). We then need to mark the regions that were free on the removing device as free in the new locations, and also obsolete in the mapping entry. This method preserves the fragmentation of the removing device, rather than consolidating its allocated space into a small number of chunks where possible. But it results in drastic reduction of memory used by the mapping table - around 20x in the most-fragmented cases. In the most fragmented real-world cases, this reduces memory used by the mapping from ~1GB to ~50MB of RAM per 1TB of storage removed. Less fragmented cases will typically also see around 50-100MB of RAM per 1TB of storage. Porting notes: * Add the following as module parameters: * zfs_condense_indirect_vdevs_enable * zfs_condense_max_obsolete_bytes * Document the following module parameters: * zfs_condense_indirect_vdevs_enable * zfs_condense_max_obsolete_bytes * zfs_condense_min_mapping_bytes Authored by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Tim Chase <tim@chase2k.com> OpenZFS-issue: https://illumos.org/issues/9486 OpenZFS-commit: https://github.com/ahrens/illumos/commit/07152e142e44c External-issue: DLPX-57962 Closes #7536
2018-02-27 02:33:55 +03:00
.sp
.ne 2
.na
\fBzfs_condense_indirect_vdevs_enable\fR (int)
.ad
.RS 12n
Enable condensing indirect vdev mappings. When set to a non-zero value,
attempt to condense indirect vdev mappings if the mapping uses more than
\fBzfs_condense_min_mapping_bytes\fR bytes of memory and if the obsolete
space map object uses more than \fBzfs_condense_max_obsolete_bytes\fR
bytes on-disk. The condensing process is an attempt to save memory by
removing obsolete mappings.
.sp
Default value: \fB1\fR.
.RE
.sp
.ne 2
.na
\fBzfs_condense_max_obsolete_bytes\fR (ulong)
.ad
.RS 12n
Only attempt to condense indirect vdev mappings if the on-disk size
of the obsolete space map object is greater than this number of bytes
(see \fBfBzfs_condense_indirect_vdevs_enable\fR).
.sp
Default value: \fB1,073,741,824\fR.
.RE
.sp
.ne 2
.na
\fBzfs_condense_min_mapping_bytes\fR (ulong)
.ad
.RS 12n
Minimum size vdev mapping to attempt to condense (see
\fBzfs_condense_indirect_vdevs_enable\fR).
.sp
Default value: \fB131,072\fR.
.RE
Add dbgmsg kstat Internally ZFS keeps a small log to facilitate debugging. By default the log is disabled, to enable it set zfs_dbgmsg_enable=1. The contents of the log can be accessed by reading the /proc/spl/kstat/zfs/dbgmsg file. Writing 0 to this proc file clears the log. $ echo 1 >/sys/module/zfs/parameters/zfs_dbgmsg_enable $ echo 0 >/proc/spl/kstat/zfs/dbgmsg $ zpool import tank $ cat /proc/spl/kstat/zfs/dbgmsg 1 0 0x01 -1 0 2492357525542 2525836565501 timestamp message 1441141408 spa=tank async request task=1 1441141408 txg 70 open pool version 5000; software version 5000/5; ... 1441141409 spa=tank async request task=32 1441141409 txg 72 import pool version 5000; software version 5000/5; ... 1441141414 command: lt-zpool import tank Note the zfs_dbgmsg() and dprintf() functions are both now mapped to the same log. As mentioned above the kernel debug log can be accessed though the /proc/spl/kstat/zfs/dbgmsg kstat. For user space consumers log messages are immediately written to stdout after applying the ZFS_DEBUG environment variable. $ ZFS_DEBUG=on ./cmd/ztest/ztest -V Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Ned Bass <bass6@llnl.gov> Closes #3728
2015-09-01 23:19:10 +03:00
.sp
.ne 2
.na
\fBzfs_dbgmsg_enable\fR (int)
.ad
.RS 12n
Internally ZFS keeps a small log to facilitate debugging. By default the log
is disabled, to enable it set this option to 1. The contents of the log can
be accessed by reading the /proc/spl/kstat/zfs/dbgmsg file. Writing 0 to
this proc file clears the log.
.sp
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
\fBzfs_dbgmsg_maxsize\fR (int)
.ad
.RS 12n
The maximum size in bytes of the internal ZFS debug log.
.sp
Default value: \fB4M\fR.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
.ne 2
.na
\fBzfs_dbuf_state_index\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
This feature is currently unused. It is normally used for controlling what
reporting is available under /proc/spl/kstat/zfs.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
\fBzfs_deadman_enabled\fR (int)
.ad
.RS 12n
Update deadman operation to better align with upstream OpenZFS The deadman in ZoL didn't behave quite as it did in upstream OpenZFS. In addition to the 2 purposes for which OpenZFS used the zfs_deadman_synctime_ms parameter, ZoL also used it to determine how frequently the deadman would fire once it has been triggered. This patch adds the zfs_deadman_checktime_ms parameter to control how frequently the subsequent checks are performed. The deadman is now disabled for suspended pools. As had been the case, unlike upstream OpenZFS, ZoL will not panic when a hung IO is detected. The module parameter documentation has been upated to include the new parameter and to better describe the operation of the deadmen. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: George Melikov <mail@gmelikov.ru> Signed-off-by: Tim Chase <tim@chase2k.com> Closes #5695
2017-02-01 01:19:08 +03:00
When a pool sync operation takes longer than \fBzfs_deadman_synctime_ms\fR
Extend deadman logic The intent of this patch is extend the existing deadman code such that it's flexible enough to be used by both ztest and on production systems. The proposed changes include: * Added a new `zfs_deadman_failmode` module option which is used to dynamically control the behavior of the deadman. It's loosely modeled after, but independant from, the pool failmode property. It can be set to wait, continue, or panic. * wait - Wait for the "hung" I/O (default) * continue - Attempt to recover from a "hung" I/O * panic - Panic the system * Added a new `zfs_deadman_ziotime_ms` module option which is analogous to `zfs_deadman_synctime_ms` except instead of applying to a pool TXG sync it applies to zio_wait(). A default value of 300s is used to define a "hung" zio. * The ztest deadman thread has been re-enabled by default, aligned with the upstream OpenZFS code, and then extended to terminate the process when it takes significantly longer to complete than expected. * The -G option was added to ztest to print the internal debug log when a fatal error is encountered. This same option was previously added to zdb in commit fa603f82. Update zloop.sh to unconditionally pass -G to obtain additional debugging. * The FM_EREPORT_ZFS_DELAY event which was previously posted when the deadman detect a "hung" pool has been replaced by a new dedicated FM_EREPORT_ZFS_DEADMAN event. * The proposed recovery logic attempts to restart a "hung" zio by calling zio_interrupt() on any outstanding leaf zios. We may want to further restrict this to zios in either the ZIO_STAGE_VDEV_IO_START or ZIO_STAGE_VDEV_IO_DONE stages. Calling zio_interrupt() is expected to only be useful for cases when an IO has been submitted to the physical device but for some reasonable the completion callback hasn't been called by the lower layers. This shouldn't be possible but has been observed and may be caused by kernel/driver bugs. * The 'zfs_deadman_synctime_ms' default value was reduced from 1000s to 600s. * Depending on how ztest fails there may be no cache file to move. This should not be considered fatal, collect the logs which are available and carry on. * Add deadman test cases for spa_deadman() and zio_wait(). * Increase default zfs_deadman_checktime_ms to 60s. Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed by: Thomas Caputi <tcaputi@datto.com> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #6999
2017-12-19 01:06:07 +03:00
milliseconds, or when an individual I/O takes longer than
\fBzfs_deadman_ziotime_ms\fR milliseconds, then the operation is considered to
be "hung". If \fBzfs_deadman_enabled\fR is set then the deadman behavior is
invoked as described by the \fBzfs_deadman_failmode\fR module option.
By default the deadman is enabled and configured to \fBwait\fR which results
in "hung" I/Os only being logged. The deadman is automatically disabled
when a pool gets suspended.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Extend deadman logic The intent of this patch is extend the existing deadman code such that it's flexible enough to be used by both ztest and on production systems. The proposed changes include: * Added a new `zfs_deadman_failmode` module option which is used to dynamically control the behavior of the deadman. It's loosely modeled after, but independant from, the pool failmode property. It can be set to wait, continue, or panic. * wait - Wait for the "hung" I/O (default) * continue - Attempt to recover from a "hung" I/O * panic - Panic the system * Added a new `zfs_deadman_ziotime_ms` module option which is analogous to `zfs_deadman_synctime_ms` except instead of applying to a pool TXG sync it applies to zio_wait(). A default value of 300s is used to define a "hung" zio. * The ztest deadman thread has been re-enabled by default, aligned with the upstream OpenZFS code, and then extended to terminate the process when it takes significantly longer to complete than expected. * The -G option was added to ztest to print the internal debug log when a fatal error is encountered. This same option was previously added to zdb in commit fa603f82. Update zloop.sh to unconditionally pass -G to obtain additional debugging. * The FM_EREPORT_ZFS_DELAY event which was previously posted when the deadman detect a "hung" pool has been replaced by a new dedicated FM_EREPORT_ZFS_DEADMAN event. * The proposed recovery logic attempts to restart a "hung" zio by calling zio_interrupt() on any outstanding leaf zios. We may want to further restrict this to zios in either the ZIO_STAGE_VDEV_IO_START or ZIO_STAGE_VDEV_IO_DONE stages. Calling zio_interrupt() is expected to only be useful for cases when an IO has been submitted to the physical device but for some reasonable the completion callback hasn't been called by the lower layers. This shouldn't be possible but has been observed and may be caused by kernel/driver bugs. * The 'zfs_deadman_synctime_ms' default value was reduced from 1000s to 600s. * Depending on how ztest fails there may be no cache file to move. This should not be considered fatal, collect the logs which are available and carry on. * Add deadman test cases for spa_deadman() and zio_wait(). * Increase default zfs_deadman_checktime_ms to 60s. Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed by: Thomas Caputi <tcaputi@datto.com> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #6999
2017-12-19 01:06:07 +03:00
Default value: \fB1\fR.
.RE
.sp
.ne 2
.na
\fBzfs_deadman_failmode\fR (charp)
.ad
.RS 12n
Controls the failure behavior when the deadman detects a "hung" I/O. Valid
values are \fBwait\fR, \fBcontinue\fR, and \fBpanic\fR.
.sp
\fBwait\fR - Wait for a "hung" I/O to complete. For each "hung" I/O a
"deadman" event will be posted describing that I/O.
.sp
\fBcontinue\fR - Attempt to recover from a "hung" I/O by re-dispatching it
to the I/O pipeline if possible.
.sp
\fBpanic\fR - Panic the system. This can be used to facilitate an automatic
fail-over to a properly configured fail-over partner.
.sp
Default value: \fBwait\fR.
Update deadman operation to better align with upstream OpenZFS The deadman in ZoL didn't behave quite as it did in upstream OpenZFS. In addition to the 2 purposes for which OpenZFS used the zfs_deadman_synctime_ms parameter, ZoL also used it to determine how frequently the deadman would fire once it has been triggered. This patch adds the zfs_deadman_checktime_ms parameter to control how frequently the subsequent checks are performed. The deadman is now disabled for suspended pools. As had been the case, unlike upstream OpenZFS, ZoL will not panic when a hung IO is detected. The module parameter documentation has been upated to include the new parameter and to better describe the operation of the deadmen. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: George Melikov <mail@gmelikov.ru> Signed-off-by: Tim Chase <tim@chase2k.com> Closes #5695
2017-02-01 01:19:08 +03:00
.RE
.sp
.ne 2
.na
\fBzfs_deadman_checktime_ms\fR (int)
.ad
.RS 12n
Extend deadman logic The intent of this patch is extend the existing deadman code such that it's flexible enough to be used by both ztest and on production systems. The proposed changes include: * Added a new `zfs_deadman_failmode` module option which is used to dynamically control the behavior of the deadman. It's loosely modeled after, but independant from, the pool failmode property. It can be set to wait, continue, or panic. * wait - Wait for the "hung" I/O (default) * continue - Attempt to recover from a "hung" I/O * panic - Panic the system * Added a new `zfs_deadman_ziotime_ms` module option which is analogous to `zfs_deadman_synctime_ms` except instead of applying to a pool TXG sync it applies to zio_wait(). A default value of 300s is used to define a "hung" zio. * The ztest deadman thread has been re-enabled by default, aligned with the upstream OpenZFS code, and then extended to terminate the process when it takes significantly longer to complete than expected. * The -G option was added to ztest to print the internal debug log when a fatal error is encountered. This same option was previously added to zdb in commit fa603f82. Update zloop.sh to unconditionally pass -G to obtain additional debugging. * The FM_EREPORT_ZFS_DELAY event which was previously posted when the deadman detect a "hung" pool has been replaced by a new dedicated FM_EREPORT_ZFS_DEADMAN event. * The proposed recovery logic attempts to restart a "hung" zio by calling zio_interrupt() on any outstanding leaf zios. We may want to further restrict this to zios in either the ZIO_STAGE_VDEV_IO_START or ZIO_STAGE_VDEV_IO_DONE stages. Calling zio_interrupt() is expected to only be useful for cases when an IO has been submitted to the physical device but for some reasonable the completion callback hasn't been called by the lower layers. This shouldn't be possible but has been observed and may be caused by kernel/driver bugs. * The 'zfs_deadman_synctime_ms' default value was reduced from 1000s to 600s. * Depending on how ztest fails there may be no cache file to move. This should not be considered fatal, collect the logs which are available and carry on. * Add deadman test cases for spa_deadman() and zio_wait(). * Increase default zfs_deadman_checktime_ms to 60s. Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed by: Thomas Caputi <tcaputi@datto.com> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #6999
2017-12-19 01:06:07 +03:00
Check time in milliseconds. This defines the frequency at which we check
for hung I/O and potentially invoke the \fBzfs_deadman_failmode\fR behavior.
Update deadman operation to better align with upstream OpenZFS The deadman in ZoL didn't behave quite as it did in upstream OpenZFS. In addition to the 2 purposes for which OpenZFS used the zfs_deadman_synctime_ms parameter, ZoL also used it to determine how frequently the deadman would fire once it has been triggered. This patch adds the zfs_deadman_checktime_ms parameter to control how frequently the subsequent checks are performed. The deadman is now disabled for suspended pools. As had been the case, unlike upstream OpenZFS, ZoL will not panic when a hung IO is detected. The module parameter documentation has been upated to include the new parameter and to better describe the operation of the deadmen. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: George Melikov <mail@gmelikov.ru> Signed-off-by: Tim Chase <tim@chase2k.com> Closes #5695
2017-02-01 01:19:08 +03:00
.sp
Extend deadman logic The intent of this patch is extend the existing deadman code such that it's flexible enough to be used by both ztest and on production systems. The proposed changes include: * Added a new `zfs_deadman_failmode` module option which is used to dynamically control the behavior of the deadman. It's loosely modeled after, but independant from, the pool failmode property. It can be set to wait, continue, or panic. * wait - Wait for the "hung" I/O (default) * continue - Attempt to recover from a "hung" I/O * panic - Panic the system * Added a new `zfs_deadman_ziotime_ms` module option which is analogous to `zfs_deadman_synctime_ms` except instead of applying to a pool TXG sync it applies to zio_wait(). A default value of 300s is used to define a "hung" zio. * The ztest deadman thread has been re-enabled by default, aligned with the upstream OpenZFS code, and then extended to terminate the process when it takes significantly longer to complete than expected. * The -G option was added to ztest to print the internal debug log when a fatal error is encountered. This same option was previously added to zdb in commit fa603f82. Update zloop.sh to unconditionally pass -G to obtain additional debugging. * The FM_EREPORT_ZFS_DELAY event which was previously posted when the deadman detect a "hung" pool has been replaced by a new dedicated FM_EREPORT_ZFS_DEADMAN event. * The proposed recovery logic attempts to restart a "hung" zio by calling zio_interrupt() on any outstanding leaf zios. We may want to further restrict this to zios in either the ZIO_STAGE_VDEV_IO_START or ZIO_STAGE_VDEV_IO_DONE stages. Calling zio_interrupt() is expected to only be useful for cases when an IO has been submitted to the physical device but for some reasonable the completion callback hasn't been called by the lower layers. This shouldn't be possible but has been observed and may be caused by kernel/driver bugs. * The 'zfs_deadman_synctime_ms' default value was reduced from 1000s to 600s. * Depending on how ztest fails there may be no cache file to move. This should not be considered fatal, collect the logs which are available and carry on. * Add deadman test cases for spa_deadman() and zio_wait(). * Increase default zfs_deadman_checktime_ms to 60s. Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed by: Thomas Caputi <tcaputi@datto.com> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #6999
2017-12-19 01:06:07 +03:00
Default value: \fB60,000\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.RE
.sp
.ne 2
.na
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 07:01:20 +04:00
\fBzfs_deadman_synctime_ms\fR (ulong)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.ad
.RS 12n
Update deadman operation to better align with upstream OpenZFS The deadman in ZoL didn't behave quite as it did in upstream OpenZFS. In addition to the 2 purposes for which OpenZFS used the zfs_deadman_synctime_ms parameter, ZoL also used it to determine how frequently the deadman would fire once it has been triggered. This patch adds the zfs_deadman_checktime_ms parameter to control how frequently the subsequent checks are performed. The deadman is now disabled for suspended pools. As had been the case, unlike upstream OpenZFS, ZoL will not panic when a hung IO is detected. The module parameter documentation has been upated to include the new parameter and to better describe the operation of the deadmen. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: George Melikov <mail@gmelikov.ru> Signed-off-by: Tim Chase <tim@chase2k.com> Closes #5695
2017-02-01 01:19:08 +03:00
Interval in milliseconds after which the deadman is triggered and also
Extend deadman logic The intent of this patch is extend the existing deadman code such that it's flexible enough to be used by both ztest and on production systems. The proposed changes include: * Added a new `zfs_deadman_failmode` module option which is used to dynamically control the behavior of the deadman. It's loosely modeled after, but independant from, the pool failmode property. It can be set to wait, continue, or panic. * wait - Wait for the "hung" I/O (default) * continue - Attempt to recover from a "hung" I/O * panic - Panic the system * Added a new `zfs_deadman_ziotime_ms` module option which is analogous to `zfs_deadman_synctime_ms` except instead of applying to a pool TXG sync it applies to zio_wait(). A default value of 300s is used to define a "hung" zio. * The ztest deadman thread has been re-enabled by default, aligned with the upstream OpenZFS code, and then extended to terminate the process when it takes significantly longer to complete than expected. * The -G option was added to ztest to print the internal debug log when a fatal error is encountered. This same option was previously added to zdb in commit fa603f82. Update zloop.sh to unconditionally pass -G to obtain additional debugging. * The FM_EREPORT_ZFS_DELAY event which was previously posted when the deadman detect a "hung" pool has been replaced by a new dedicated FM_EREPORT_ZFS_DEADMAN event. * The proposed recovery logic attempts to restart a "hung" zio by calling zio_interrupt() on any outstanding leaf zios. We may want to further restrict this to zios in either the ZIO_STAGE_VDEV_IO_START or ZIO_STAGE_VDEV_IO_DONE stages. Calling zio_interrupt() is expected to only be useful for cases when an IO has been submitted to the physical device but for some reasonable the completion callback hasn't been called by the lower layers. This shouldn't be possible but has been observed and may be caused by kernel/driver bugs. * The 'zfs_deadman_synctime_ms' default value was reduced from 1000s to 600s. * Depending on how ztest fails there may be no cache file to move. This should not be considered fatal, collect the logs which are available and carry on. * Add deadman test cases for spa_deadman() and zio_wait(). * Increase default zfs_deadman_checktime_ms to 60s. Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed by: Thomas Caputi <tcaputi@datto.com> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #6999
2017-12-19 01:06:07 +03:00
the interval after which a pool sync operation is considered to be "hung".
Once this limit is exceeded the deadman will be invoked every
\fBzfs_deadman_checktime_ms\fR milliseconds until the pool sync completes.
.sp
Default value: \fB600,000\fR.
.RE
Update deadman operation to better align with upstream OpenZFS The deadman in ZoL didn't behave quite as it did in upstream OpenZFS. In addition to the 2 purposes for which OpenZFS used the zfs_deadman_synctime_ms parameter, ZoL also used it to determine how frequently the deadman would fire once it has been triggered. This patch adds the zfs_deadman_checktime_ms parameter to control how frequently the subsequent checks are performed. The deadman is now disabled for suspended pools. As had been the case, unlike upstream OpenZFS, ZoL will not panic when a hung IO is detected. The module parameter documentation has been upated to include the new parameter and to better describe the operation of the deadmen. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: George Melikov <mail@gmelikov.ru> Signed-off-by: Tim Chase <tim@chase2k.com> Closes #5695
2017-02-01 01:19:08 +03:00
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Extend deadman logic The intent of this patch is extend the existing deadman code such that it's flexible enough to be used by both ztest and on production systems. The proposed changes include: * Added a new `zfs_deadman_failmode` module option which is used to dynamically control the behavior of the deadman. It's loosely modeled after, but independant from, the pool failmode property. It can be set to wait, continue, or panic. * wait - Wait for the "hung" I/O (default) * continue - Attempt to recover from a "hung" I/O * panic - Panic the system * Added a new `zfs_deadman_ziotime_ms` module option which is analogous to `zfs_deadman_synctime_ms` except instead of applying to a pool TXG sync it applies to zio_wait(). A default value of 300s is used to define a "hung" zio. * The ztest deadman thread has been re-enabled by default, aligned with the upstream OpenZFS code, and then extended to terminate the process when it takes significantly longer to complete than expected. * The -G option was added to ztest to print the internal debug log when a fatal error is encountered. This same option was previously added to zdb in commit fa603f82. Update zloop.sh to unconditionally pass -G to obtain additional debugging. * The FM_EREPORT_ZFS_DELAY event which was previously posted when the deadman detect a "hung" pool has been replaced by a new dedicated FM_EREPORT_ZFS_DEADMAN event. * The proposed recovery logic attempts to restart a "hung" zio by calling zio_interrupt() on any outstanding leaf zios. We may want to further restrict this to zios in either the ZIO_STAGE_VDEV_IO_START or ZIO_STAGE_VDEV_IO_DONE stages. Calling zio_interrupt() is expected to only be useful for cases when an IO has been submitted to the physical device but for some reasonable the completion callback hasn't been called by the lower layers. This shouldn't be possible but has been observed and may be caused by kernel/driver bugs. * The 'zfs_deadman_synctime_ms' default value was reduced from 1000s to 600s. * Depending on how ztest fails there may be no cache file to move. This should not be considered fatal, collect the logs which are available and carry on. * Add deadman test cases for spa_deadman() and zio_wait(). * Increase default zfs_deadman_checktime_ms to 60s. Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed by: Thomas Caputi <tcaputi@datto.com> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #6999
2017-12-19 01:06:07 +03:00
.ne 2
.na
\fBzfs_deadman_ziotime_ms\fR (ulong)
.ad
.RS 12n
Interval in milliseconds after which the deadman is triggered and an
individual IO operation is considered to be "hung". As long as the I/O
remains "hung" the deadman will be invoked every \fBzfs_deadman_checktime_ms\fR
milliseconds until the I/O completes.
.sp
Default value: \fB300,000\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.RE
.sp
.ne 2
.na
\fBzfs_dedup_prefetch\fR (int)
.ad
.RS 12n
Enable prefetching dedup-ed blks
.sp
Change the default 'zfs_dedup_prefetch' value to '0' This gives a huge performance improvement in operations with deduped datasets especially when the bottleneck is the amount of ram available for zfs. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2639
2014-08-30 06:13:26 +04:00
Use \fB1\fR for yes and \fB0\fR to disable (default).
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.RE
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 07:01:20 +04:00
.sp
.ne 2
.na
\fBzfs_delay_min_dirty_percent\fR (int)
.ad
.RS 12n
Start to delay each transaction once there is this amount of dirty data,
expressed as a percentage of \fBzfs_dirty_data_max\fR.
This value should be >= zfs_vdev_async_write_active_max_dirty_percent.
See the section "ZFS TRANSACTION DELAY".
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 22:51:11 +03:00
Default value: \fB60\fR%.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 07:01:20 +04:00
.RE
.sp
.ne 2
.na
\fBzfs_delay_scale\fR (int)
.ad
.RS 12n
This controls how quickly the transaction delay approaches infinity.
Larger values cause longer delays for a given amount of dirty data.
.sp
For the smoothest delay, this value should be about 1 billion divided
by the maximum number of operations per second. This will smoothly
handle between 10x and 1/10th this number.
.sp
See the section "ZFS TRANSACTION DELAY".
.sp
Note: \fBzfs_delay_scale\fR * \fBzfs_dirty_data_max\fR must be < 2^64.
.sp
Default value: \fB500,000\fR.
.RE
Change checksum & IO delay ratelimit values Change checksum & IO delay ratelimit thresholds from 5/sec to 20/sec. This allows zed to actually trigger if a bunch of these events arrive in a short period of time (zed has a threshold of 10 events in 10 sec). Previously, if you had, say, 100 checksum errors in 1 sec, it would get ratelimited to 5/sec which wouldn't trigger zed to fault the drive. Also, convert the checksum and IO delay thresholds to module params for easy testing. Reviewed-by: loli10K <ezomori.nozomu@gmail.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Tony Hutter <hutter2@llnl.gov> Closes #7252
2018-03-05 04:34:51 +03:00
.sp
.ne 2
.na
\fBzfs_delays_per_second\fR (int)
.ad
.RS 12n
Rate limit IO delay events to this many per second.
.sp
Default value: 20
.RE
Reintroduce zfs_remove() synchronous deletes Reintroduce a slightly adapted version of the Illumos logic for synchronous unlinks. The basic idea here is that only files smaller than zfs_delete_blocks (20480) blocks should be deleted synchronously. Unlinking larger files should be handled asynchronously to minimize impact to the caller. To accomplish this iput() which is responsible for calling zfs_znode_delete() on Linux is only called in the delete_now path. Otherwise zfs_async_iput() is used which allows the last reference to be dropped by a taskq thread effectively making the removal asynchronous. Porting notes: - Add zfs_delete_blocks module option for performance analysis. The default value is DMU_MAX_DELETEBLKCNT which is the same as upstream. Reducing this value means that smaller files will be unlinked asynchronously like large files. - All occurrences of zfsvfs changes to zsb. Ported-by: KernelOfTruth kerneloftruth@gmail.com Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2015-08-21 04:43:10 +03:00
.sp
.ne 2
.na
\fBzfs_delete_blocks\fR (ulong)
.ad
.RS 12n
This is the used to define a large file for the purposes of delete. Files
containing more than \fBzfs_delete_blocks\fR will be deleted asynchronously
while smaller files are deleted synchronously. Decreasing this value will
reduce the time spent in an unlink(2) system call at the expense of a longer
delay before the freed space is available.
.sp
Default value: \fB20,480\fR.
.RE
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 07:01:20 +04:00
.sp
.ne 2
.na
\fBzfs_dirty_data_max\fR (int)
.ad
.RS 12n
Determines the dirty space limit in bytes. Once this limit is exceeded, new
writes are halted until space frees up. This parameter takes precedence
over \fBzfs_dirty_data_max_percent\fR.
See the section "ZFS TRANSACTION DELAY".
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 22:51:11 +03:00
Default value: \fB10\fR% of physical RAM, capped at \fBzfs_dirty_data_max_max\fR.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 07:01:20 +04:00
.RE
.sp
.ne 2
.na
\fBzfs_dirty_data_max_max\fR (int)
.ad
.RS 12n
Maximum allowable value of \fBzfs_dirty_data_max\fR, expressed in bytes.
This limit is only enforced at module load time, and will be ignored if
\fBzfs_dirty_data_max\fR is later changed. This parameter takes
precedence over \fBzfs_dirty_data_max_max_percent\fR. See the section
"ZFS TRANSACTION DELAY".
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 22:51:11 +03:00
Default value: \fB25\fR% of physical RAM.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 07:01:20 +04:00
.RE
.sp
.ne 2
.na
\fBzfs_dirty_data_max_max_percent\fR (int)
.ad
.RS 12n
Maximum allowable value of \fBzfs_dirty_data_max\fR, expressed as a
percentage of physical RAM. This limit is only enforced at module load
time, and will be ignored if \fBzfs_dirty_data_max\fR is later changed.
The parameter \fBzfs_dirty_data_max_max\fR takes precedence over this
one. See the section "ZFS TRANSACTION DELAY".
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 22:51:11 +03:00
Default value: \fB25\fR%.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 07:01:20 +04:00
.RE
.sp
.ne 2
.na
\fBzfs_dirty_data_max_percent\fR (int)
.ad
.RS 12n
Determines the dirty space limit, expressed as a percentage of all
memory. Once this limit is exceeded, new writes are halted until space frees
up. The parameter \fBzfs_dirty_data_max\fR takes precedence over this
one. See the section "ZFS TRANSACTION DELAY".
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 22:51:11 +03:00
Default value: \fB10\fR%, subject to \fBzfs_dirty_data_max_max\fR.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 07:01:20 +04:00
.RE
.sp
.ne 2
.na
OpenZFS 9617 - too-frequent TXG sync causes excessive write inflation Porting notes: * Renamed zfs_dirty_data_sync_pct to zfs_dirty_data_sync_percent and changed the type to be consistent with the other dirty module params. * Updated zfs-module-parameters.5 accordingly. Authored by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com> Reviewed by: Brad Lewis <brad.lewis@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Andrew Stormont <andyjstormont@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Approved by: Robert Mustacchi <rm@joyent.com> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://illumos.org/issues/9617 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/7928f4ba Closes #7976
2017-12-13 02:46:58 +03:00
\fBzfs_dirty_data_sync_percent\fR (int)
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 07:01:20 +04:00
.ad
.RS 12n
OpenZFS 9617 - too-frequent TXG sync causes excessive write inflation Porting notes: * Renamed zfs_dirty_data_sync_pct to zfs_dirty_data_sync_percent and changed the type to be consistent with the other dirty module params. * Updated zfs-module-parameters.5 accordingly. Authored by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com> Reviewed by: Brad Lewis <brad.lewis@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Andrew Stormont <andyjstormont@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Approved by: Robert Mustacchi <rm@joyent.com> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://illumos.org/issues/9617 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/7928f4ba Closes #7976
2017-12-13 02:46:58 +03:00
Start syncing out a transaction group if there's at least this much dirty data
as a percentage of \fBzfs_dirty_data_max\fR. This should be less than
\fBzfs_vdev_async_write_active_min_dirty_percent\fR.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 07:01:20 +04:00
.sp
OpenZFS 9617 - too-frequent TXG sync causes excessive write inflation Porting notes: * Renamed zfs_dirty_data_sync_pct to zfs_dirty_data_sync_percent and changed the type to be consistent with the other dirty module params. * Updated zfs-module-parameters.5 accordingly. Authored by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com> Reviewed by: Brad Lewis <brad.lewis@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Andrew Stormont <andyjstormont@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Approved by: Robert Mustacchi <rm@joyent.com> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://illumos.org/issues/9617 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/7928f4ba Closes #7976
2017-12-13 02:46:58 +03:00
Default value: \fB20\fR% of \fBzfs_dirty_data_max\fR.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 07:01:20 +04:00
.RE
Implementation of AVX2 optimized Fletcher-4 New functionality: - Preserves existing scalar implementation. - Adds AVX2 optimized Fletcher-4 computation. - Fastest routines selected on module load (benchmark). - Test case for Fletcher-4 added to ztest. New zcommon module parameters: - zfs_fletcher_4_impl (str): selects the implementation to use. "fastest" - use the fastest version available "cycle" - cycle trough all available impl for ztest "scalar" - use the original version "avx2" - new AVX2 implementation if available Performance comparison (Intel i7 CPU, 1MB data buffers): - Scalar: 4216 MB/s - AVX2: 14499 MB/s See contents of `/sys/module/zcommon/parameters/zfs_fletcher_4_impl` to get list of supported values. If an implementation is not supported on the system, it will not be shown. Currently selected option is enclosed in `[]`. Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com> Signed-off-by: Andreas Dilger <andreas.dilger@intel.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4330
2015-12-10 02:34:16 +03:00
.sp
.ne 2
.na
\fBzfs_fletcher_4_impl\fR (string)
.ad
.RS 12n
Select a fletcher 4 implementation.
.sp
Implementation of SSE optimized Fletcher-4 Builds off of 1eeb4562 (Implementation of AVX2 optimized Fletcher-4) This commit adds another implementation of the Fletcher-4 algorithm. It is automatically selected at module load if it benchmarks higher than all other available implementations. The module benchmark was also amended to analyze the performance of the byteswap-ed version of Fletcher-4, as well as the non-byteswaped version. The average performance of the two is used to select the the fastest implementation available on the host system. Adds a pair of fields to an existing zcommon module parameter: - zfs_fletcher_4_impl (str) "sse2" - new SSE2 implementation if available "ssse3" - new SSSE3 implementation if available Signed-off-by: Tyler J. Stachecki <stachecki.tyler@gmail.com> Signed-off-by: Gvozden Neskovic <neskovic@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4789
2016-06-24 06:32:40 +03:00
Supported selectors are: \fBfastest\fR, \fBscalar\fR, \fBsse2\fR, \fBssse3\fR,
Fletcher4 algorithm implemented in pure NEON for Aarch64 / ARMv8 64 bits This is not useful on micro-architecture with a weak NEON implementation (only 64 bits); the native version is slower & the byteswap barely faster than scalar. On A53 or A57, it's a small improvement on scalar but OK for byteswap. Results from an A53 system: 0 0 0x01 -1 0 1499068294333000 1499101101878000 implementation native byteswap scalar 1008227510 755880264 aarch64_neon 1198098720 1044818671 fastest aarch64_neon aarch64_neon Results from a A57 system: 0 0 0x01 -1 0 4407214734807033 4407233933777404 implementation native byteswap scalar 2302071241 1124873346 aarch64_neon 2542214946 2245570352 fastest aarch64_neon aarch64_neon Reviewed-by: Gvozden Neskovic <neskovic@gmail.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Romain Dolbeau <romain.dolbeau@atos.net> Closes #5248
2016-10-21 20:55:49 +03:00
\fBavx2\fR, \fBavx512f\fR, and \fBaarch64_neon\fR.
Fletcher4 implementation using avx512f instruction set Algorithm runs 8 parallel sums, consuming 8x uint32_t elements per loop iteration. Size alignment of main fletcher4 methods is adjusted accordingly. New implementation is called 'avx512f'. Note: byteswap method can be implemented more efficiently when avx512bw hardware becomes available. Currently, it is ~ 2x slower than native method. Table shows result of full (native) fletcher4 calculation for different buffer size: fletcher4 4KB 16KB 64KB 128KB 256KB 1MB 16MB -------------------------------------------------------------------- [scalar] 1213 1228 1231 1231 1225 1200 1160 [sse2] 2374 2442 2459 2456 2462 2250 2220 [avx2] 4288 4753 4871 4893 4900 4050 3882 [avx512f] 5975 8445 9196 9221 9262 6307 5620 Signed-off-by: Gvozden Neskovic <neskovic@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #4952
2016-07-06 14:42:04 +03:00
All of the selectors except \fBfastest\fR and \fBscalar\fR require instruction
set extensions to be available and will only appear if ZFS detects that they are
present at runtime. If multiple implementations of fletcher 4 are available,
the \fBfastest\fR will be chosen using a micro benchmark. Selecting \fBscalar\fR
results in the original, CPU based calculation, being used. Selecting any option
other than \fBfastest\fR and \fBscalar\fR results in vector instructions from
the respective CPU instruction set being used.
Implementation of AVX2 optimized Fletcher-4 New functionality: - Preserves existing scalar implementation. - Adds AVX2 optimized Fletcher-4 computation. - Fastest routines selected on module load (benchmark). - Test case for Fletcher-4 added to ztest. New zcommon module parameters: - zfs_fletcher_4_impl (str): selects the implementation to use. "fastest" - use the fastest version available "cycle" - cycle trough all available impl for ztest "scalar" - use the original version "avx2" - new AVX2 implementation if available Performance comparison (Intel i7 CPU, 1MB data buffers): - Scalar: 4216 MB/s - AVX2: 14499 MB/s See contents of `/sys/module/zcommon/parameters/zfs_fletcher_4_impl` to get list of supported values. If an implementation is not supported on the system, it will not be shown. Currently selected option is enclosed in `[]`. Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com> Signed-off-by: Andreas Dilger <andreas.dilger@intel.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4330
2015-12-10 02:34:16 +03:00
.sp
Default value: \fBfastest\fR.
.RE
Illumos 6251 - add tunable to disable free_bpobj processing 6251 - add tunable to disable free_bpobj processing Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Simon Klinkert <simon.klinkert@gmail.com> Reviewed by: Richard Elling <Richard.Elling@RichardElling.com> Reviewed by: Albert Lee <trisk@omniti.com> Reviewed by: Xin Li <delphij@freebsd.org> Approved by: Garrett D'Amore <garrett@damore.org> References: https://www.illumos.org/issues/6251 https://github.com/illumos/illumos-gate/commit/139510f Porting notes: - Added as module option declaration. - Added to zfs-module-parameters.5 man page. Ported-by: Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2016-01-23 03:41:02 +03:00
.sp
.ne 2
.na
\fBzfs_free_bpobj_enabled\fR (int)
.ad
.RS 12n
Enable/disable the processing of the free_bpobj object.
.sp
Default value: \fB1\fR.
.RE
Illumos 5138 - add tunable for maximum number of blocks freed in one txg Reviewed by: Adam Leventhal <adam.leventhal@delphix.com> Reviewed by: Mattew Ahrens <mahrens@delphix.com> Reviewed by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net> Reviewed by: Richard Elling <richard.elling@gmail.com> Reviewed by: George Wilson <george.wilson@delphix.com> Approved by: Dan McDonald <danmcd@omniti.com> References: https://www.illumos.org/issues/5138 https://github.com/illumos/illumos-gate/commit/af3465d Porting notes: Because support for exposing a uint64_t parameter wasn't added until v3.17-rc1 the zfs_free_max_blocks variable has been declared as a unsigned long. This is already far larger than required and it allows us to avoid additional autoconf compatibility code. The default value has been set to 100,000 on Linux instead of ULONG_MAX which is used on Illumos. This was done to limit the number of outstanding IOs in the system when snapshots are destroyed. This helps ensure individual TXG sync times are kept reasonable and memory isn't wasted managing a huge backlog of outstanding IOs. Ported by: Turbo Fredriksson <turbo@bayour.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2675 Closes #2581
2014-09-07 19:06:08 +04:00
.sp
.ne 2
.na
OpenZFS 7614, 9064 - zfs device evacuation/removal OpenZFS 7614 - zfs device evacuation/removal OpenZFS 9064 - remove_mirror should wait for device removal to complete This project allows top-level vdevs to be removed from the storage pool with "zpool remove", reducing the total amount of storage in the pool. This operation copies all allocated regions of the device to be removed onto other devices, recording the mapping from old to new location. After the removal is complete, read and free operations to the removed (now "indirect") vdev must be remapped and performed at the new location on disk. The indirect mapping table is kept in memory whenever the pool is loaded, so there is minimal performance overhead when doing operations on the indirect vdev. The size of the in-memory mapping table will be reduced when its entries become "obsolete" because they are no longer used by any block pointers in the pool. An entry becomes obsolete when all the blocks that use it are freed. An entry can also become obsolete when all the snapshots that reference it are deleted, and the block pointers that reference it have been "remapped" in all filesystems/zvols (and clones). Whenever an indirect block is written, all the block pointers in it will be "remapped" to their new (concrete) locations if possible. This process can be accelerated by using the "zfs remap" command to proactively rewrite all indirect blocks that reference indirect (removed) vdevs. Note that when a device is removed, we do not verify the checksum of the data that is copied. This makes the process much faster, but if it were used on redundant vdevs (i.e. mirror or raidz vdevs), it would be possible to copy the wrong data, when we have the correct data on e.g. the other side of the mirror. At the moment, only mirrors and simple top-level vdevs can be removed and no removal is allowed if any of the top-level vdevs are raidz. Porting Notes: * Avoid zero-sized kmem_alloc() in vdev_compact_children(). The device evacuation code adds a dependency that vdev_compact_children() be able to properly empty the vdev_child array by setting it to NULL and zeroing vdev_children. Under Linux, kmem_alloc() and related functions return a sentinel pointer rather than NULL for zero-sized allocations. * Remove comment regarding "mpt" driver where zfs_remove_max_segment is initialized to SPA_MAXBLOCKSIZE. Change zfs_condense_indirect_commit_entry_delay_ticks to zfs_condense_indirect_commit_entry_delay_ms for consistency with most other tunables in which delays are specified in ms. * ZTS changes: Use set_tunable rather than mdb Use zpool sync as appropriate Use sync_pool instead of sync Kill jobs during test_removal_with_operation to allow unmount/export Don't add non-disk names such as "mirror" or "raidz" to $DISKS Use $TEST_BASE_DIR instead of /tmp Increase HZ from 100 to 1000 which is more common on Linux removal_multiple_indirection.ksh Reduce iterations in order to not time out on the code coverage builders. removal_resume_export: Functionally, the test case is correct but there exists a race where the kernel thread hasn't been fully started yet and is not visible. Wait for up to 1 second for the removal thread to be started before giving up on it. Also, increase the amount of data copied in order that the removal not finish before the export has a chance to fail. * MMP compatibility, the concept of concrete versus non-concrete devices has slightly changed the semantics of vdev_writeable(). Update mmp_random_leaf_impl() accordingly. * Updated dbuf_remap() to handle the org.zfsonlinux:large_dnode pool feature which is not supported by OpenZFS. * Added support for new vdev removal tracepoints. * Test cases removal_with_zdb and removal_condense_export have been intentionally disabled. When run manually they pass as intended, but when running in the automated test environment they produce unreliable results on the latest Fedora release. They may work better once the upstream pool import refectoring is merged into ZoL at which point they will be re-enabled. Authored by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Alex Reece <alex@delphix.com> Reviewed-by: George Wilson <george.wilson@delphix.com> Reviewed-by: John Kennedy <john.kennedy@delphix.com> Reviewed-by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Richard Laager <rlaager@wiktel.com> Reviewed by: Tim Chase <tim@chase2k.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Garrett D'Amore <garrett@damore.org> Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Tim Chase <tim@chase2k.com> OpenZFS-issue: https://www.illumos.org/issues/7614 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/f539f1eb Closes #6900
2016-09-22 19:30:13 +03:00
\fBzfs_async_block_max_blocks\fR (ulong)
Illumos 5138 - add tunable for maximum number of blocks freed in one txg Reviewed by: Adam Leventhal <adam.leventhal@delphix.com> Reviewed by: Mattew Ahrens <mahrens@delphix.com> Reviewed by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net> Reviewed by: Richard Elling <richard.elling@gmail.com> Reviewed by: George Wilson <george.wilson@delphix.com> Approved by: Dan McDonald <danmcd@omniti.com> References: https://www.illumos.org/issues/5138 https://github.com/illumos/illumos-gate/commit/af3465d Porting notes: Because support for exposing a uint64_t parameter wasn't added until v3.17-rc1 the zfs_free_max_blocks variable has been declared as a unsigned long. This is already far larger than required and it allows us to avoid additional autoconf compatibility code. The default value has been set to 100,000 on Linux instead of ULONG_MAX which is used on Illumos. This was done to limit the number of outstanding IOs in the system when snapshots are destroyed. This helps ensure individual TXG sync times are kept reasonable and memory isn't wasted managing a huge backlog of outstanding IOs. Ported by: Turbo Fredriksson <turbo@bayour.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2675 Closes #2581
2014-09-07 19:06:08 +04:00
.ad
.RS 12n
Maximum number of blocks freed in a single txg.
.sp
Default value: \fB100,000\fR.
.RE
OpenZFS 9256 - zfs send space estimation off by > 10% on some datasets Authored by: Paul Dagnelie <pcd@delphix.com> Reviewed by: Matt Ahrens <matt@delphix.com> Reviewed by: John Kennedy <john.kennedy@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Richard Lowe <richlowe@richlowe.net> Ported-by: Giuseppe Di Natale <dinatale2@llnl.gov> Porting Notes: * Added tuning to man page. * Test case changes dropped, default behavior unchanged. OpenZFS-issue: https://www.illumos.org/issues/9256 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/32356b3c56 Closes #7470
2016-08-26 21:43:21 +03:00
.sp
.ne 2
.na
\fBzfs_override_estimate_recordsize\fR (ulong)
.ad
.RS 12n
Record size calculation override for zfs send estimates.
.sp
Default value: \fB0\fR.
.RE
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 07:01:20 +04:00
.sp
.ne 2
.na
\fBzfs_vdev_async_read_max_active\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Maximum asynchronous read I/Os active to each device.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 07:01:20 +04:00
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB3\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_async_read_min_active\fR (int)
.ad
.RS 12n
Minimum asynchronous read I/Os active to each device.
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB1\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_async_write_active_max_dirty_percent\fR (int)
.ad
.RS 12n
When the pool has more than
\fBzfs_vdev_async_write_active_max_dirty_percent\fR dirty data, use
\fBzfs_vdev_async_write_max_active\fR to limit active async writes. If
the dirty data is between min and max, the active I/O limit is linearly
interpolated. See the section "ZFS I/O SCHEDULER".
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 22:51:11 +03:00
Default value: \fB60\fR%.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 07:01:20 +04:00
.RE
.sp
.ne 2
.na
\fBzfs_vdev_async_write_active_min_dirty_percent\fR (int)
.ad
.RS 12n
When the pool has less than
\fBzfs_vdev_async_write_active_min_dirty_percent\fR dirty data, use
\fBzfs_vdev_async_write_min_active\fR to limit active async writes. If
the dirty data is between min and max, the active I/O limit is linearly
interpolated. See the section "ZFS I/O SCHEDULER".
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 22:51:11 +03:00
Default value: \fB30\fR%.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 07:01:20 +04:00
.RE
.sp
.ne 2
.na
\fBzfs_vdev_async_write_max_active\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Maximum asynchronous write I/Os active to each device.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 07:01:20 +04:00
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB10\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_async_write_min_active\fR (int)
.ad
.RS 12n
Minimum asynchronous write I/Os active to each device.
See the section "ZFS I/O SCHEDULER".
.sp
Increase zfs_vdev_async_write_min_active to 2 Resilver operations frequently cause only a small amount of dirty data to be written to disk at a time, resulting in the IO scheduler to only issue 1 write at a time to the resilvering disk. When it is rotational media the drive will often travel past the next sector to be written before receiving a write command from ZFS, significantly delaying the write of the next sector. Raise zfs_vdev_async_write_min_active so that drives are kept fed during resilvering. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: DHE <git@dehacked.net> Issue #4825 Closes #5926
2017-03-26 05:36:28 +03:00
Lower values are associated with better latency on rotational media but poorer
resilver performance. The default value of 2 was chosen as a compromise. A
value of 3 has been shown to improve resilver performance further at a cost of
further increasing latency.
.sp
Default value: \fB2\fR.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 07:01:20 +04:00
.RE
.sp
.ne 2
.na
\fBzfs_vdev_max_active\fR (int)
.ad
.RS 12n
The maximum number of I/Os active to each device. Ideally, this will be >=
the sum of each queue's max_active. It must be at least the sum of each
queue's min_active. See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB1,000\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_scrub_max_active\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Maximum scrub I/Os active to each device.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 07:01:20 +04:00
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB2\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_scrub_min_active\fR (int)
.ad
.RS 12n
Minimum scrub I/Os active to each device.
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB1\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_sync_read_max_active\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Maximum synchronous read I/Os active to each device.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 07:01:20 +04:00
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB10\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_sync_read_min_active\fR (int)
.ad
.RS 12n
Minimum synchronous read I/Os active to each device.
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB10\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_sync_write_max_active\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Maximum synchronous write I/Os active to each device.
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 07:01:20 +04:00
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB10\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_sync_write_min_active\fR (int)
.ad
.RS 12n
Minimum synchronous write I/Os active to each device.
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB10\fR.
.RE
OpenZFS 7090 - zfs should throttle allocations OpenZFS 7090 - zfs should throttle allocations Authored by: George Wilson <george.wilson@delphix.com> Reviewed by: Alex Reece <alex@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Paul Dagnelie <paul.dagnelie@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Sebastien Roy <sebastien.roy@delphix.com> Approved by: Matthew Ahrens <mahrens@delphix.com> Ported-by: Don Brady <don.brady@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> When write I/Os are issued, they are issued in block order but the ZIO pipeline will drive them asynchronously through the allocation stage which can result in blocks being allocated out-of-order. It would be nice to preserve as much of the logical order as possible. In addition, the allocations are equally scattered across all top-level VDEVs but not all top-level VDEVs are created equally. The pipeline should be able to detect devices that are more capable of handling allocations and should allocate more blocks to those devices. This allows for dynamic allocation distribution when devices are imbalanced as fuller devices will tend to be slower than empty devices. The change includes a new pool-wide allocation queue which would throttle and order allocations in the ZIO pipeline. The queue would be ordered by issued time and offset and would provide an initial amount of allocation of work to each top-level vdev. The allocation logic utilizes a reservation system to reserve allocations that will be performed by the allocator. Once an allocation is successfully completed it's scheduled on a given top-level vdev. Each top-level vdev maintains a maximum number of allocations that it can handle (mg_alloc_queue_depth). The pool-wide reserved allocations (top-levels * mg_alloc_queue_depth) are distributed across the top-level vdevs metaslab groups and round robin across all eligible metaslab groups to distribute the work. As top-levels complete their work, they receive additional work from the pool-wide allocation queue until the allocation queue is emptied. OpenZFS-issue: https://www.illumos.org/issues/7090 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/4756c3d7 Closes #5258 Porting Notes: - Maintained minimal stack in zio_done - Preserve linux-specific io sizes in zio_write_compress - Added module params and documentation - Updated to use optimize AVL cmp macros
2016-10-14 03:59:18 +03:00
.sp
.ne 2
.na
\fBzfs_vdev_queue_depth_pct\fR (int)
.ad
.RS 12n
Update documentation for zfs_vdev_queue_depth_pct It was documented as being related to zfs_vdev_async_max_active when it is actually related to zfs_vdev_async_write_max_active. Also, expand the documentation to describe the allocation throttle which was introduced as part of OpenZFS 7090 in 3dfb57a. Reviewed-by: Richard Yao <ryao@gentoo.org> Reviewed-by: Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Tim Chase <tim@chase2k.com> Closes #6064
2017-04-25 07:01:04 +03:00
Maximum number of queued allocations per top-level vdev expressed as
a percentage of \fBzfs_vdev_async_write_max_active\fR which allows the
system to detect devices that are more capable of handling allocations
and to allocate more blocks to those devices. It allows for dynamic
allocation distribution when devices are imbalanced as fuller devices
will tend to be slower than empty devices.
See also \fBzio_dva_throttle_enabled\fR.
OpenZFS 7090 - zfs should throttle allocations OpenZFS 7090 - zfs should throttle allocations Authored by: George Wilson <george.wilson@delphix.com> Reviewed by: Alex Reece <alex@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Paul Dagnelie <paul.dagnelie@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Sebastien Roy <sebastien.roy@delphix.com> Approved by: Matthew Ahrens <mahrens@delphix.com> Ported-by: Don Brady <don.brady@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> When write I/Os are issued, they are issued in block order but the ZIO pipeline will drive them asynchronously through the allocation stage which can result in blocks being allocated out-of-order. It would be nice to preserve as much of the logical order as possible. In addition, the allocations are equally scattered across all top-level VDEVs but not all top-level VDEVs are created equally. The pipeline should be able to detect devices that are more capable of handling allocations and should allocate more blocks to those devices. This allows for dynamic allocation distribution when devices are imbalanced as fuller devices will tend to be slower than empty devices. The change includes a new pool-wide allocation queue which would throttle and order allocations in the ZIO pipeline. The queue would be ordered by issued time and offset and would provide an initial amount of allocation of work to each top-level vdev. The allocation logic utilizes a reservation system to reserve allocations that will be performed by the allocator. Once an allocation is successfully completed it's scheduled on a given top-level vdev. Each top-level vdev maintains a maximum number of allocations that it can handle (mg_alloc_queue_depth). The pool-wide reserved allocations (top-levels * mg_alloc_queue_depth) are distributed across the top-level vdevs metaslab groups and round robin across all eligible metaslab groups to distribute the work. As top-levels complete their work, they receive additional work from the pool-wide allocation queue until the allocation queue is emptied. OpenZFS-issue: https://www.illumos.org/issues/7090 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/4756c3d7 Closes #5258 Porting Notes: - Maintained minimal stack in zio_done - Preserve linux-specific io sizes in zio_write_compress - Added module params and documentation - Updated to use optimize AVL cmp macros
2016-10-14 03:59:18 +03:00
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 22:51:11 +03:00
Default value: \fB1000\fR%.
OpenZFS 7090 - zfs should throttle allocations OpenZFS 7090 - zfs should throttle allocations Authored by: George Wilson <george.wilson@delphix.com> Reviewed by: Alex Reece <alex@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Paul Dagnelie <paul.dagnelie@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Sebastien Roy <sebastien.roy@delphix.com> Approved by: Matthew Ahrens <mahrens@delphix.com> Ported-by: Don Brady <don.brady@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> When write I/Os are issued, they are issued in block order but the ZIO pipeline will drive them asynchronously through the allocation stage which can result in blocks being allocated out-of-order. It would be nice to preserve as much of the logical order as possible. In addition, the allocations are equally scattered across all top-level VDEVs but not all top-level VDEVs are created equally. The pipeline should be able to detect devices that are more capable of handling allocations and should allocate more blocks to those devices. This allows for dynamic allocation distribution when devices are imbalanced as fuller devices will tend to be slower than empty devices. The change includes a new pool-wide allocation queue which would throttle and order allocations in the ZIO pipeline. The queue would be ordered by issued time and offset and would provide an initial amount of allocation of work to each top-level vdev. The allocation logic utilizes a reservation system to reserve allocations that will be performed by the allocator. Once an allocation is successfully completed it's scheduled on a given top-level vdev. Each top-level vdev maintains a maximum number of allocations that it can handle (mg_alloc_queue_depth). The pool-wide reserved allocations (top-levels * mg_alloc_queue_depth) are distributed across the top-level vdevs metaslab groups and round robin across all eligible metaslab groups to distribute the work. As top-levels complete their work, they receive additional work from the pool-wide allocation queue until the allocation queue is emptied. OpenZFS-issue: https://www.illumos.org/issues/7090 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/4756c3d7 Closes #5258 Porting Notes: - Maintained minimal stack in zio_done - Preserve linux-specific io sizes in zio_write_compress - Added module params and documentation - Updated to use optimize AVL cmp macros
2016-10-14 03:59:18 +03:00
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
.ne 2
.na
\fBzfs_expire_snapshot\fR (int)
.ad
.RS 12n
Seconds to expire .zfs/snapshot
.sp
Default value: \fB300\fR.
.RE
Support accessing .zfs/snapshot via NFS This patch is based on the previous work done by @andrey-ve and @yshui. It triggers the automount by using kern_path() to traverse to the known snapshout mount point. Once the snapshot is mounted NFS can access the contents of the snapshot. Allowing NFS clients to access to the .zfs/snapshot directory would normally mean that a root user on a client mounting an export with 'no_root_squash' would be able to use mkdir/rmdir/mv to manipulate snapshots on the server. To prevent configuration mistakes a zfs_admin_snapshot module option was added which disables the mkdir/rmdir/mv functionally. System administators desiring this functionally must explicitly enable it. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2797 Closes #1655 Closes #616
2015-08-29 00:54:32 +03:00
.sp
.ne 2
.na
\fBzfs_admin_snapshot\fR (int)
.ad
.RS 12n
Allow the creation, removal, or renaming of entries in the .zfs/snapshot
directory to cause the creation, destruction, or renaming of snapshots.
When enabled this functionality works both locally and over NFS exports
which have the 'no_root_squash' option set. This functionality is disabled
by default.
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
.ne 2
.na
\fBzfs_flags\fR (int)
.ad
.RS 12n
Document zfs_flags module parameter Add a table describing the debugging flags that can be set in the zfs_flags module parameter. Also change the module_param type to 'uint' so users aren't shown a negative value. The updated man page text is reproduced below for convenience. zfs_flags (int) Set additional debugging flags. The following flags may be bitwise-or'd together. +-------------------------------------------------------+ |Value Symbolic Name | | Description | +-------------------------------------------------------+ | 1 ZFS_DEBUG_DPRINTF | | Enable dprintf entries in the debug log. | +-------------------------------------------------------+ | 2 ZFS_DEBUG_DBUF_VERIFY * | | Enable extra dbuf verifications. | +-------------------------------------------------------+ | 4 ZFS_DEBUG_DNODE_VERIFY * | | Enable extra dnode verifications. | +-------------------------------------------------------+ | 8 ZFS_DEBUG_SNAPNAMES | | Enable snapshot name verification. | +-------------------------------------------------------+ | 16 ZFS_DEBUG_MODIFY | | Check for illegally modified ARC buffers. | +-------------------------------------------------------+ | 32 ZFS_DEBUG_SPA | | Enable spa_dbgmsg entries in the debug log. | +-------------------------------------------------------+ | 64 ZFS_DEBUG_ZIO_FREE | | Enable verification of block frees. | +-------------------------------------------------------+ | 128 ZFS_DEBUG_HISTOGRAM_VERIFY | | Enable extra spacemap histogram verifications. | +-------------------------------------------------------+ * Requires debug build. Default value: 0. Signed-off-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2988
2014-12-23 03:54:43 +03:00
Set additional debugging flags. The following flags may be bitwise-or'd
together.
.sp
.TS
box;
rB lB
lB lB
r l.
Value Symbolic Name
Description
_
1 ZFS_DEBUG_DPRINTF
Enable dprintf entries in the debug log.
_
2 ZFS_DEBUG_DBUF_VERIFY *
Enable extra dbuf verifications.
_
4 ZFS_DEBUG_DNODE_VERIFY *
Enable extra dnode verifications.
_
8 ZFS_DEBUG_SNAPNAMES
Enable snapshot name verification.
_
16 ZFS_DEBUG_MODIFY
Check for illegally modified ARC buffers.
_
64 ZFS_DEBUG_ZIO_FREE
Enable verification of block frees.
_
128 ZFS_DEBUG_HISTOGRAM_VERIFY
Enable extra spacemap histogram verifications.
Add line info and SET_ERROR() to ZFS debug log Redefine the SET_ERROR macro in terms of __dprintf() so the error return codes get logged as both tracepoint events (if tracepoints are enabled) and as ZFS debug log entries. This also allows us to use the same definition of SET_ERROR() in kernel and user space. Define a new debug flag ZFS_DEBUG_SET_ERROR=512 that may be bitwise or'd into zfs_flags. Setting this flag enables both dprintf() and SET_ERROR() messages in the debug log. That is, setting ZFS_DEBUG_SET_ERROR and ZFS_DEBUG_DPRINTF|ZFS_DEBUG_SET_ERROR are equivalent (this was done for sake of simplicity). Leaving ZFS_DEBUG_SET_ERROR unset suppresses the SET_ERROR() messages which helps avoid cluttering up the logs. To enable SET_ERROR() logging, run: echo 1 > /sys/module/zfs/parameters/zfs_dbgmsg_enable echo 512 > /sys/module/zfs/parameters/zfs_flags Remove the zfs_set_error_class tracepoints event class since SET_ERROR() now uses __dprintf(). This sacrifices a bit of granularity when selecting individual tracepoint events to enable but it makes the code simpler. Include file, function, and line number information in debug log entries. The information is now added to the message buffer in __dprintf() and as a result the zfs_dprintf_class tracepoints event class was changed from a 4 parameter interface to a single parameter. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Ned Bass <bass6@llnl.gov> Closes #6400
2017-07-26 09:09:48 +03:00
_
256 ZFS_DEBUG_METASLAB_VERIFY
Verify space accounting on disk matches in-core range_trees.
_
512 ZFS_DEBUG_SET_ERROR
Enable SET_ERROR and dprintf entries in the debug log.
Document zfs_flags module parameter Add a table describing the debugging flags that can be set in the zfs_flags module parameter. Also change the module_param type to 'uint' so users aren't shown a negative value. The updated man page text is reproduced below for convenience. zfs_flags (int) Set additional debugging flags. The following flags may be bitwise-or'd together. +-------------------------------------------------------+ |Value Symbolic Name | | Description | +-------------------------------------------------------+ | 1 ZFS_DEBUG_DPRINTF | | Enable dprintf entries in the debug log. | +-------------------------------------------------------+ | 2 ZFS_DEBUG_DBUF_VERIFY * | | Enable extra dbuf verifications. | +-------------------------------------------------------+ | 4 ZFS_DEBUG_DNODE_VERIFY * | | Enable extra dnode verifications. | +-------------------------------------------------------+ | 8 ZFS_DEBUG_SNAPNAMES | | Enable snapshot name verification. | +-------------------------------------------------------+ | 16 ZFS_DEBUG_MODIFY | | Check for illegally modified ARC buffers. | +-------------------------------------------------------+ | 32 ZFS_DEBUG_SPA | | Enable spa_dbgmsg entries in the debug log. | +-------------------------------------------------------+ | 64 ZFS_DEBUG_ZIO_FREE | | Enable verification of block frees. | +-------------------------------------------------------+ | 128 ZFS_DEBUG_HISTOGRAM_VERIFY | | Enable extra spacemap histogram verifications. | +-------------------------------------------------------+ * Requires debug build. Default value: 0. Signed-off-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2988
2014-12-23 03:54:43 +03:00
.TE
.sp
* Requires debug build.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Document zfs_flags module parameter Add a table describing the debugging flags that can be set in the zfs_flags module parameter. Also change the module_param type to 'uint' so users aren't shown a negative value. The updated man page text is reproduced below for convenience. zfs_flags (int) Set additional debugging flags. The following flags may be bitwise-or'd together. +-------------------------------------------------------+ |Value Symbolic Name | | Description | +-------------------------------------------------------+ | 1 ZFS_DEBUG_DPRINTF | | Enable dprintf entries in the debug log. | +-------------------------------------------------------+ | 2 ZFS_DEBUG_DBUF_VERIFY * | | Enable extra dbuf verifications. | +-------------------------------------------------------+ | 4 ZFS_DEBUG_DNODE_VERIFY * | | Enable extra dnode verifications. | +-------------------------------------------------------+ | 8 ZFS_DEBUG_SNAPNAMES | | Enable snapshot name verification. | +-------------------------------------------------------+ | 16 ZFS_DEBUG_MODIFY | | Check for illegally modified ARC buffers. | +-------------------------------------------------------+ | 32 ZFS_DEBUG_SPA | | Enable spa_dbgmsg entries in the debug log. | +-------------------------------------------------------+ | 64 ZFS_DEBUG_ZIO_FREE | | Enable verification of block frees. | +-------------------------------------------------------+ | 128 ZFS_DEBUG_HISTOGRAM_VERIFY | | Enable extra spacemap histogram verifications. | +-------------------------------------------------------+ * Requires debug build. Default value: 0. Signed-off-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2988
2014-12-23 03:54:43 +03:00
Default value: \fB0\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.RE
Illumos 4390 - I/O errors can corrupt space map when deleting fs/vol 4390 i/o errors when deleting filesystem/zvol can lead to space map corruption Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Dan McDonald <danmcd@omniti.com> Reviewed by: Saso Kiselkov <saso.kiselkov@nexenta.com> Approved by: Dan McDonald <danmcd@omniti.com> References: https://www.illumos.org/issues/4390 https://github.com/illumos/illumos-gate/commit/7fd05ac Porting notes: Previous stack-reduction efforts in traverse_visitb() caused a fair number of un-mergable pieces of code. This patch should reduce its stack footprint a bit more. The new local bptree_entry_phys_t in bptree_add() is dynamically-allocated using kmem_zalloc() for the purpose of stack reduction. The new global zfs_free_leak_on_eio has been defined as an integer rather than a boolean_t as was the case with the related zfs_recover global. Also, zfs_free_leak_on_eio's definition has been inserted into zfs_debug.c for consistency with the existing definition of zfs_recover. Illumos placed it in spa_misc.c. Ported by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2545
2014-06-06 01:20:08 +04:00
.sp
.ne 2
.na
\fBzfs_free_leak_on_eio\fR (int)
.ad
.RS 12n
If destroy encounters an EIO while reading metadata (e.g. indirect
blocks), space referenced by the missing metadata can not be freed.
Normally this causes the background destroy to become "stalled", as
it is unable to make forward progress. While in this stalled state,
all remaining space to free from the error-encountering filesystem is
"temporarily leaked". Set this flag to cause it to ignore the EIO,
permanently leak the space from indirect blocks that can not be read,
and continue to free everything else that it can.
The default, "stalling" behavior is useful if the storage partially
fails (i.e. some but not all i/os fail), and then later recovers. In
this case, we will be able to continue pool operations while it is
partially failed, and when it recovers, we can continue to free the
space, with no leaks. However, note that this case is actually
fairly rare.
Typically pools either (a) fail completely (but perhaps temporarily,
e.g. a top-level vdev going offline), or (b) have localized,
permanent errors (e.g. disk returns the wrong data due to bit flip or
firmware bug). In case (a), this setting does not matter because the
pool will be suspended and the sync thread will not be able to make
forward progress regardless. In case (b), because the error is
permanent, the best we can do is leak the minimum amount of space,
which is what setting this flag will do. Therefore, it is reasonable
for this flag to normally be set, but we chose the more conservative
approach of not setting it, so that there is no possibility of
leaking space in the "partial temporary" failure case.
.sp
Default value: \fB0\fR.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
.ne 2
.na
\fBzfs_free_min_time_ms\fR (int)
.ad
.RS 12n
Fix man page formatting in zfs-module-parameters Bold and Normal codes were mixed up in a few places resulting in bad highlighting. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: DHE <git@dehacked.net> Closes #5397
2016-11-15 04:03:57 +03:00
During a \fBzfs destroy\fR operation using \fBfeature@async_destroy\fR a minimum
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
of this much time will be spent working on freeing blocks per txg.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Default value: \fB1,000\fR.
.RE
.sp
.ne 2
.na
\fBzfs_immediate_write_sz\fR (long)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Largest data block to write to zil. Larger blocks will be treated as if the
Fix man page formatting in zfs-module-parameters Bold and Normal codes were mixed up in a few places resulting in bad highlighting. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: DHE <git@dehacked.net> Closes #5397
2016-11-15 04:03:57 +03:00
dataset being written to had the property setting \fBlogbias=throughput\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Default value: \fB32,768\fR.
.RE
Add tunables for channel programs This patch adds tunables for modifying the maximum memory limit and maximum instruction limit that can be specified when running a channel program. Reviewed-by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov Reviewed-by: Sara Hartse <sara.hartse@delphix.com> Signed-off-by: John Gallagher <john.gallagher@delphix.com> External-issue: LX-1085 Closes #7618
2018-06-16 01:10:42 +03:00
.sp
.ne 2
.na
\fBzfs_lua_max_instrlimit\fR (ulong)
.ad
.RS 12n
The maximum execution time limit that can be set for a ZFS channel program,
specified as a number of Lua instructions.
.sp
Default value: \fB100,000,000\fR.
.RE
.sp
.ne 2
.na
\fBzfs_lua_max_memlimit\fR (ulong)
.ad
.RS 12n
The maximum memory limit that can be set for a ZFS channel program, specified
in bytes.
.sp
Default value: \fB104,857,600\fR.
.RE
OpenZFS 9330 - stack overflow when creating a deeply nested dataset Datasets that are deeply nested (~100 levels) are impractical. We just put a limit of 50 levels to newly created datasets. Existing datasets should work without a problem. The problem can be seen by attempting to create a dataset using the -p option with many levels: panic[cpu0]/thread=ffffff01cd282c20: BAD TRAP: type=8 (#df Double fault) rp=ffffffff fffffffffbc3aa60 unix:die+100 () fffffffffbc3ab70 unix:trap+157d () ffffff00083d7020 unix:_patch_xrstorq_rbx+196 () ffffff00083d7050 zfs:dbuf_rele+2e () ... ffffff00083d7080 zfs:dsl_dir_close+32 () ffffff00083d70b0 zfs:dsl_dir_evict+30 () ffffff00083d70d0 zfs:dbuf_evict_user+4a () ffffff00083d7100 zfs:dbuf_rele_and_unlock+87 () ffffff00083d7130 zfs:dbuf_rele+2e () ... The block above repeats once per directory in the ... ... create -p command, working towards the root ... ffffff00083db9f0 zfs:dsl_dataset_drop_ref+19 () ffffff00083dba20 zfs:dsl_dataset_rele+42 () ffffff00083dba70 zfs:dmu_objset_prefetch+e4 () ffffff00083dbaa0 zfs:findfunc+23 () ffffff00083dbb80 zfs:dmu_objset_find_spa+38c () ffffff00083dbbc0 zfs:dmu_objset_find+40 () ffffff00083dbc20 zfs:zfs_ioc_snapshot_list_next+4b () ffffff00083dbcc0 zfs:zfsdev_ioctl+347 () ffffff00083dbd00 genunix:cdev_ioctl+45 () ffffff00083dbd40 specfs:spec_ioctl+5a () ffffff00083dbdc0 genunix:fop_ioctl+7b () ffffff00083dbec0 genunix:ioctl+18e () ffffff00083dbf10 unix:brand_sys_sysenter+1c9 () Porting notes: * Added zfs_max_dataset_nesting module option with documentation. * Updated zfs_rename_014_neg.ksh for Linux. * Increase the zfs.sh stack warning to 15K. Enough time has passed that 16K can be reasonably assumed to be the default value. It was increased in the 3.15 kernel released in June of 2014. Authored by: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com> Reviewed by: John Kennedy <john.kennedy@delphix.com> Reviewed by: Matt Ahrens <matt@delphix.com> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Garrett D'Amore <garrett@damore.org> OpenZFS-issue: https://www.illumos.org/issues/9330 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/757a75a Closes #7681
2016-09-12 18:15:20 +03:00
.sp
.ne 2
.na
\fBzfs_max_dataset_nesting\fR (int)
.ad
.RS 12n
The maximum depth of nested datasets. This value can be tuned temporarily to
fix existing datasets that exceed the predefined limit.
.sp
Default value: \fB50\fR.
.RE
Illumos 5027 - zfs large block support 5027 zfs large block support Reviewed by: Alek Pinchuk <pinchuk.alek@gmail.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Josef 'Jeff' Sipek <josef.sipek@nexenta.com> Reviewed by: Richard Elling <richard.elling@richardelling.com> Reviewed by: Saso Kiselkov <skiselkov.ml@gmail.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Dan McDonald <danmcd@omniti.com> References: https://www.illumos.org/issues/5027 https://github.com/illumos/illumos-gate/commit/b515258 Porting Notes: * Included in this patch is a tiny ISP2() cleanup in zio_init() from Illumos 5255. * Unlike the upstream Illumos commit this patch does not impose an arbitrary 128K block size limit on volumes. Volumes, like filesystems, are limited by the zfs_max_recordsize=1M module option. * By default the maximum record size is limited to 1M by the module option zfs_max_recordsize. This value may be safely increased up to 16M which is the largest block size supported by the on-disk format. At the moment, 1M blocks clearly offer a significant performance improvement but the benefits of going beyond this for the majority of workloads are less clear. * The illumos version of this patch increased DMU_MAX_ACCESS to 32M. This was determined not to be large enough when using 16M blocks because the zfs_make_xattrdir() function will fail (EFBIG) when assigning a TX. This was immediately observed under Linux because all newly created files must have a security xattr created and that was failing. Therefore, we've set DMU_MAX_ACCESS to 64M. * On 32-bit platforms a hard limit of 1M is set for blocks due to the limited virtual address space. We should be able to relax this one the ABD patches are merged. Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #354
2014-11-03 23:15:08 +03:00
.sp
.ne 2
.na
\fBzfs_max_recordsize\fR (int)
.ad
.RS 12n
We currently support block sizes from 512 bytes to 16MB. The benefits of
larger blocks, and thus larger IO, need to be weighed against the cost of
COWing a giant block to modify one byte. Additionally, very large blocks
can have an impact on i/o latency, and also potentially on the memory
allocator. Therefore, we do not allow the recordsize to be set larger than
zfs_max_recordsize (default 1MB). Larger blocks can be created by changing
this tunable, and pools with larger blocks can always be imported and used,
regardless of this setting.
.sp
Default value: \fB1,048,576\fR.
.RE
Illumos 4976-4984 - metaslab improvements 4976 zfs should only avoid writing to a failing non-redundant top-level vdev 4978 ztest fails in get_metaslab_refcount() 4979 extend free space histogram to device and pool 4980 metaslabs should have a fragmentation metric 4981 remove fragmented ops vector from block allocator 4982 space_map object should proactively upgrade when feature is enabled 4983 need to collect metaslab information via mdb 4984 device selection should use fragmentation metric Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Adam Leventhal <adam.leventhal@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Approved by: Garrett D'Amore <garrett@damore.org> References: https://www.illumos.org/issues/4976 https://www.illumos.org/issues/4978 https://www.illumos.org/issues/4979 https://www.illumos.org/issues/4980 https://www.illumos.org/issues/4981 https://www.illumos.org/issues/4982 https://www.illumos.org/issues/4983 https://www.illumos.org/issues/4984 https://github.com/illumos/illumos-gate/commit/2e4c998 Notes: The "zdb -M" option has been re-tasked to display the new metaslab fragmentation metric and the new "zdb -I" option is used to control the maximum number of in-flight I/Os. The new fragmentation metric is derived from the space map histogram which has been rolled up to the vdev and pool level and is presented to the user via "zpool list". Add a number of module parameters related to the new metaslab weighting logic. Ported by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2595
2014-07-20 00:19:24 +04:00
.sp
.ne 2
.na
\fBzfs_metaslab_fragmentation_threshold\fR (int)
.ad
.RS 12n
Allow metaslabs to keep their active state as long as their fragmentation
percentage is less than or equal to this value. An active metaslab that
exceeds this threshold will no longer keep its active status allowing
better metaslabs to be selected.
.sp
Default value: \fB70\fR.
.RE
.sp
.ne 2
.na
\fBzfs_mg_fragmentation_threshold\fR (int)
.ad
.RS 12n
Metaslab groups are considered eligible for allocations if their
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
fragmentation metric (measured as a percentage) is less than or equal to
Illumos 4976-4984 - metaslab improvements 4976 zfs should only avoid writing to a failing non-redundant top-level vdev 4978 ztest fails in get_metaslab_refcount() 4979 extend free space histogram to device and pool 4980 metaslabs should have a fragmentation metric 4981 remove fragmented ops vector from block allocator 4982 space_map object should proactively upgrade when feature is enabled 4983 need to collect metaslab information via mdb 4984 device selection should use fragmentation metric Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Adam Leventhal <adam.leventhal@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Approved by: Garrett D'Amore <garrett@damore.org> References: https://www.illumos.org/issues/4976 https://www.illumos.org/issues/4978 https://www.illumos.org/issues/4979 https://www.illumos.org/issues/4980 https://www.illumos.org/issues/4981 https://www.illumos.org/issues/4982 https://www.illumos.org/issues/4983 https://www.illumos.org/issues/4984 https://github.com/illumos/illumos-gate/commit/2e4c998 Notes: The "zdb -M" option has been re-tasked to display the new metaslab fragmentation metric and the new "zdb -I" option is used to control the maximum number of in-flight I/Os. The new fragmentation metric is derived from the space map histogram which has been rolled up to the vdev and pool level and is presented to the user via "zpool list". Add a number of module parameters related to the new metaslab weighting logic. Ported by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2595
2014-07-20 00:19:24 +04:00
this value. If a metaslab group exceeds this threshold then it will be
skipped unless all metaslab groups within the metaslab class have also
crossed this threshold.
.sp
Default value: \fB85\fR.
.RE
Convert zfs_mg_noalloc_threshold to a module parameter and document The parameter was added as illumos issue 4081 which was committed to zfsonlinux in ac72fac3eaa569902cad88053167f7d74e7fe7e4. This patch documents the parameter and allows for it to be set as a module parameter. Signed-off-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2483
2014-07-10 07:36:03 +04:00
.sp
.ne 2
.na
\fBzfs_mg_noalloc_threshold\fR (int)
.ad
.RS 12n
Defines a threshold at which metaslab groups should be eligible for
allocations. The value is expressed as a percentage of free space
beyond which a metaslab group is always eligible for allocations.
If a metaslab group's free space is less than or equal to the
Man page white space and spelling corrections Correct some misspelled words and grammatical errors, and remove trailing white space in the man pages. Signed-off-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4115
2015-12-17 04:45:15 +03:00
threshold, the allocator will avoid allocating to that group
Convert zfs_mg_noalloc_threshold to a module parameter and document The parameter was added as illumos issue 4081 which was committed to zfsonlinux in ac72fac3eaa569902cad88053167f7d74e7fe7e4. This patch documents the parameter and allows for it to be set as a module parameter. Signed-off-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2483
2014-07-10 07:36:03 +04:00
unless all groups in the pool have reached the threshold. Once all
groups have reached the threshold, all groups are allowed to accept
allocations. The default value of 0 disables the feature and causes
all metaslab groups to be eligible for allocations.
Man page fixes * ztest.1 man page: fix typo * zfs-module-parameters.5 man page: fix grammar Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com> Closes #6492
2017-08-11 01:45:25 +03:00
This parameter allows one to deal with pools having heavily imbalanced
Convert zfs_mg_noalloc_threshold to a module parameter and document The parameter was added as illumos issue 4081 which was committed to zfsonlinux in ac72fac3eaa569902cad88053167f7d74e7fe7e4. This patch documents the parameter and allows for it to be set as a module parameter. Signed-off-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2483
2014-07-10 07:36:03 +04:00
vdevs such as would be the case when a new vdev has been added.
Setting the threshold to a non-zero percentage will stop allocations
from being made to vdevs that aren't filled to the specified percentage
and allow lesser filled vdevs to acquire more allocations than they
otherwise would under the old \fBzfs_mg_alloc_failures\fR facility.
.sp
Default value: \fB0\fR.
.RE
Pool allocation classes Allocation Classes add the ability to have allocation classes in a pool that are dedicated to serving specific block categories, such as DDT data, metadata, and small file blocks. A pool can opt-in to this feature by adding a 'special' or 'dedup' top-level VDEV. Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com> Reviewed-by: Richard Laager <rlaager@wiktel.com> Reviewed-by: Alek Pinchuk <apinchuk@datto.com> Reviewed-by: Håkan Johansson <f96hajo@chalmers.se> Reviewed-by: Andreas Dilger <andreas.dilger@chamcloud.com> Reviewed-by: DHE <git@dehacked.net> Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com> Reviewed-by: Gregor Kopka <gregor@kopka.net> Reviewed-by: Kash Pande <kash@tripleback.net> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Matthew Ahrens <mahrens@delphix.com> Signed-off-by: Don Brady <don.brady@delphix.com> Closes #5182
2018-09-06 04:33:36 +03:00
.sp
.ne 2
.na
\fBzfs_ddt_data_is_special\fR (int)
.ad
.RS 12n
If enabled, ZFS will place DDT data into the special allocation class.
.sp
Default value: \fB1\fR.
.RE
.sp
.ne 2
.na
\fBzfs_user_indirect_is_special\fR (int)
.ad
.RS 12n
If enabled, ZFS will place user data (both file and zvol) indirect blocks
into the special allocation class.
.sp
Default value: \fB1\fR.
.RE
Multi-modifier protection (MMP) Add multihost=on|off pool property to control MMP. When enabled a new thread writes uberblocks to the last slot in each label, at a set frequency, to indicate to other hosts the pool is actively imported. These uberblocks are the last synced uberblock with an updated timestamp. Property defaults to off. During tryimport, find the "best" uberblock (newest txg and timestamp) repeatedly, checking for change in the found uberblock. Include the results of the activity test in the config returned by tryimport. These results are reported to user in "zpool import". Allow the user to control the period between MMP writes, and the duration of the activity test on import, via a new module parameter zfs_multihost_interval. The period is specified in milliseconds. The activity test duration is calculated from this value, and from the mmp_delay in the "best" uberblock found initially. Add a kstat interface to export statistics about Multiple Modifier Protection (MMP) updates. Include the last synced txg number, the timestamp, the delay since the last MMP update, the VDEV GUID, the VDEV label that received the last MMP update, and the VDEV path. Abbreviated output below. $ cat /proc/spl/kstat/zfs/mypool/multihost 31 0 0x01 10 880 105092382393521 105144180101111 txg timestamp mmp_delay vdev_guid vdev_label vdev_path 20468 261337 250274925 68396651780 3 /dev/sda 20468 261339 252023374 6267402363293 1 /dev/sdc 20468 261340 252000858 6698080955233 1 /dev/sdx 20468 261341 251980635 783892869810 2 /dev/sdy 20468 261342 253385953 8923255792467 3 /dev/sdd 20468 261344 253336622 042125143176 0 /dev/sdab 20468 261345 253310522 1200778101278 2 /dev/sde 20468 261346 253286429 0950576198362 2 /dev/sdt 20468 261347 253261545 96209817917 3 /dev/sds 20468 261349 253238188 8555725937673 3 /dev/sdb Add a new tunable zfs_multihost_history to specify the number of MMP updates to store history for. By default it is set to zero meaning that no MMP statistics are stored. When using ztest to generate activity, for automated tests of the MMP function, some test functions interfere with the test. For example, the pool is exported to run zdb and then imported again. Add a new ztest function, "-M", to alter ztest behavior to prevent this. Add new tests to verify the new functionality. Tests provided by Giuseppe Di Natale. Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Reviewed-by: Ned Bass <bass6@llnl.gov> Reviewed-by: Andreas Dilger <andreas.dilger@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Olaf Faaland <faaland1@llnl.gov> Closes #745 Closes #6279
2017-07-08 06:20:35 +03:00
.sp
.ne 2
.na
\fBzfs_multihost_history\fR (int)
.ad
.RS 12n
Historical statistics for the last N multihost updates will be available in
\fB/proc/spl/kstat/zfs/<pool>/multihost\fR
.sp
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
\fBzfs_multihost_interval\fR (ulong)
.ad
.RS 12n
Used to control the frequency of multihost writes which are performed when the
\fBmultihost\fR pool property is on. This is one factor used to determine
the length of the activity check during import.
.sp
The multihost write period is \fBzfs_multihost_interval / leaf-vdevs\fR milliseconds.
This means that on average a multihost write will be issued for each leaf vdev every
\fBzfs_multihost_interval\fR milliseconds. In practice, the observed period can
vary with the I/O load and this observed value is the delay which is stored in
the uberblock.
.sp
On import the activity check waits a minimum amount of time determined by
\fBzfs_multihost_interval * zfs_multihost_import_intervals\fR. The activity
check time may be further extended if the value of mmp delay found in the best
uberblock indicates actual multihost updates happened at longer intervals than
\fBzfs_multihost_interval\fR. A minimum value of \fB100ms\fR is enforced.
.sp
Default value: \fB1000\fR.
.RE
.sp
.ne 2
.na
\fBzfs_multihost_import_intervals\fR (uint)
.ad
.RS 12n
Used to control the duration of the activity test on import. Smaller values of
\fBzfs_multihost_import_intervals\fR will reduce the import time but increase
the risk of failing to detect an active pool. The total activity check time is
never allowed to drop below one second. A value of 0 is ignored and treated as
if it was set to 1
.sp
Default value: \fB10\fR.
.RE
.sp
.ne 2
.na
\fBzfs_multihost_fail_intervals\fR (uint)
.ad
.RS 12n
Controls the behavior of the pool when multihost write failures are detected.
.sp
When \fBzfs_multihost_fail_intervals = 0\fR then multihost write failures are ignored.
The failures will still be reported to the ZED which depending on its
configuration may take action such as suspending the pool or offlining a device.
.sp
When \fBzfs_multihost_fail_intervals > 0\fR then sequential multihost write failures
will cause the pool to be suspended. This occurs when
\fBzfs_multihost_fail_intervals * zfs_multihost_interval\fR milliseconds have
passed since the last successful multihost write. This guarantees the activity test
will see multihost writes if the pool is imported.
.sp
Default value: \fB5\fR.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
.ne 2
.na
\fBzfs_no_scrub_io\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Set for no scrub I/O. This results in scrubs not actually scrubbing data and
simply doing a metadata crawl of the pool instead.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
.sp
.ne 2
.na
\fBzfs_no_scrub_prefetch\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Set to disable block prefetching for scrubs.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
.sp
.ne 2
.na
\fBzfs_nocacheflush\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Disable cache flush operations on disks when writing. Beware, this may cause
corruption if disks re-order writes.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
.sp
.ne 2
.na
\fBzfs_nopwrite_enabled\fR (int)
.ad
.RS 12n
Enable NOP writes
.sp
Use \fB1\fR for yes (default) and \fB0\fR to disable.
.RE
SEEK_HOLE should not block on txg_wait_synced() Force flushing of txg's can be painfully slow when competing for disk IO, since this is a process meant to execute asynchronously. Optimize this path via allowing data/hole seeking if the file is clean, but if dirty fall back to old logic. This is a compromise to disabling the feature entirely. Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Debabrata Banerjee <dbanerje@akamai.com> Closes #4306 Closes #5962
2017-03-25 00:28:38 +03:00
.sp
.ne 2
.na
\fBzfs_dmu_offset_next_sync\fR (int)
.ad
.RS 12n
Enable forcing txg sync to find holes. When enabled forces ZFS to act
like prior versions when SEEK_HOLE or SEEK_DATA flags are used, which
when a dnode is dirty causes txg's to be synced so that this data can be
found.
.sp
Use \fB1\fR for yes and \fB0\fR to disable (default).
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
.ne 2
.na
Illumos 5694 - traverse_prefetcher does not prefetch enough 5694 traverse_prefetcher does not prefetch enough Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Alex Reece <alex@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Josef 'Jeff' Sipek <josef.sipek@nexenta.com> Reviewed by: Bayard Bell <buffer.g.overflow@gmail.com> Approved by: Garrett D'Amore <garrett@damore.org> References: https://www.illumos.org/issues/5694 https://github.com/illumos/illumos-gate/commit/34d7ce05 Ported-by: Chris Dunlop <chris@onthe.net.au> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #3230
2015-03-27 07:31:52 +03:00
\fBzfs_pd_bytes_max\fR (int)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
The number of bytes which should be prefetched during a pool traversal
Fix man page formatting in zfs-module-parameters Bold and Normal codes were mixed up in a few places resulting in bad highlighting. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: DHE <git@dehacked.net> Closes #5397
2016-11-15 04:03:57 +03:00
(eg: \fBzfs send\fR or other data crawling operations)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Update zfs_pd_bytes_max default in zfs(8) Commit b738bc5 should have updated the default value of zfs_pd_bytes_max in the zfs(8) man page. The correct default value is 50*1024*1024. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2015-03-31 21:51:37 +03:00
Default value: \fB52,428,800\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.RE
Add missing module_param for zfs_per_txg_dirty_frees_percent When the code was added this tunable was not exposed via module params. Also it was not documented. This patch changes the type from a uint32 to a ulong as done with other percentage tunables and also documents it in the zfs-module-parameters man page. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: David Quigley <david.quigley@intel.com> Closes #5750
2017-02-07 20:44:03 +03:00
.sp
.ne 2
.na
\fBzfs_per_txg_dirty_frees_percent \fR (ulong)
.ad
.RS 12n
Tunable to control percentage of dirtied blocks from frees in one TXG.
After this threshold is crossed, additional dirty blocks from frees
wait until the next TXG.
A value of zero will disable this throttle.
.sp
Default value: \fB30\fR and \fB0\fR to disable.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
.ne 2
.na
\fBzfs_prefetch_disable\fR (int)
.ad
.RS 12n
Illumos 5987 - zfs prefetch code needs work 5987 zfs prefetch code needs work Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Paul Dagnelie <pcd@delphix.com> Approved by: Gordon Ross <gordon.ross@nexenta.com> References: https://www.illumos.org/issues/5987 zfs prefetch code needs work illumos/illumos-gate@cf6106c 5987 zfs prefetch code needs work Porting notes: - [module/zfs/dbuf.c] - 5f6d0b6 Handle block pointers with a corrupt logical size - [module/zfs/dmu_zfetch.c] - c65aa5b Fix gcc missing parenthesis warnings - 428870f Update core ZFS code from build 121 to build 141. - 79c76d5 Change KM_PUSHPAGE -> KM_SLEEP - b8d06fc Switch KM_SLEEP to KM_PUSHPAGE - Account for ISO C90 - mixed declarations and code - warnings - Module parameters (new/changed): - Replaced zfetch_block_cap with zfetch_max_distance (Max bytes to prefetch per stream (default 8MB; 8 * 1024 * 1024)) - Preserved zfs_prefetch_disable as 'int' for consistency with existing Linux module options. - [include/sys/trace_arc.h] - Added new tracepoints - DEFINE_ARC_BUF_HDR_EVENT(zfs_arc__sync__wait__for__async); - DEFINE_ARC_BUF_HDR_EVENT(zfs_arc__demand__hit__predictive__prefetch); - [man/man5/zfs-module-parameters.5] - Updated man page Ported-by: kernelOfTruth kerneloftruth@gmail.com Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2015-12-27 00:10:31 +03:00
This tunable disables predictive prefetch. Note that it leaves "prescient"
prefetch (e.g. prefetch for zfs send) intact. Unlike predictive prefetch,
prescient prefetch never issues i/os that end up not being needed, so it
can't hurt performance.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
.sp
.ne 2
.na
\fBzfs_read_chunk_size\fR (long)
.ad
.RS 12n
Bytes to read per chunk
.sp
Default value: \fB1,048,576\fR.
.RE
.sp
.ne 2
.na
\fBzfs_read_history\fR (int)
.ad
.RS 12n
Multi-modifier protection (MMP) Add multihost=on|off pool property to control MMP. When enabled a new thread writes uberblocks to the last slot in each label, at a set frequency, to indicate to other hosts the pool is actively imported. These uberblocks are the last synced uberblock with an updated timestamp. Property defaults to off. During tryimport, find the "best" uberblock (newest txg and timestamp) repeatedly, checking for change in the found uberblock. Include the results of the activity test in the config returned by tryimport. These results are reported to user in "zpool import". Allow the user to control the period between MMP writes, and the duration of the activity test on import, via a new module parameter zfs_multihost_interval. The period is specified in milliseconds. The activity test duration is calculated from this value, and from the mmp_delay in the "best" uberblock found initially. Add a kstat interface to export statistics about Multiple Modifier Protection (MMP) updates. Include the last synced txg number, the timestamp, the delay since the last MMP update, the VDEV GUID, the VDEV label that received the last MMP update, and the VDEV path. Abbreviated output below. $ cat /proc/spl/kstat/zfs/mypool/multihost 31 0 0x01 10 880 105092382393521 105144180101111 txg timestamp mmp_delay vdev_guid vdev_label vdev_path 20468 261337 250274925 68396651780 3 /dev/sda 20468 261339 252023374 6267402363293 1 /dev/sdc 20468 261340 252000858 6698080955233 1 /dev/sdx 20468 261341 251980635 783892869810 2 /dev/sdy 20468 261342 253385953 8923255792467 3 /dev/sdd 20468 261344 253336622 042125143176 0 /dev/sdab 20468 261345 253310522 1200778101278 2 /dev/sde 20468 261346 253286429 0950576198362 2 /dev/sdt 20468 261347 253261545 96209817917 3 /dev/sds 20468 261349 253238188 8555725937673 3 /dev/sdb Add a new tunable zfs_multihost_history to specify the number of MMP updates to store history for. By default it is set to zero meaning that no MMP statistics are stored. When using ztest to generate activity, for automated tests of the MMP function, some test functions interfere with the test. For example, the pool is exported to run zdb and then imported again. Add a new ztest function, "-M", to alter ztest behavior to prevent this. Add new tests to verify the new functionality. Tests provided by Giuseppe Di Natale. Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Reviewed-by: Ned Bass <bass6@llnl.gov> Reviewed-by: Andreas Dilger <andreas.dilger@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Olaf Faaland <faaland1@llnl.gov> Closes #745 Closes #6279
2017-07-08 06:20:35 +03:00
Historical statistics for the last N reads will be available in
\fB/proc/spl/kstat/zfs/<pool>/reads\fR
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Default value: \fB0\fR (no data is kept).
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.RE
.sp
.ne 2
.na
\fBzfs_read_history_hits\fR (int)
.ad
.RS 12n
Include cache hits in read history
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
OpenZFS 9290 - device removal reduces redundancy of mirrors Mirrors are supposed to provide redundancy in the face of whole-disk failure and silent damage (e.g. some data on disk is not right, but ZFS hasn't detected the whole device as being broken). However, the current device removal implementation bypasses some of the mirror's redundancy. Note that in no case is incorrect data returned, but we might get a checksum error when we should have been able to find the right data. There are two underlying problems: 1. When we remove a mirror device, we only read one side of the mirror. Since we can't verify the checksum, this side may be silently bad, but the good data is on the other side of the mirror (which we didn't read). This can cause the removal to "bake in" the busted data – all copies of the data in the new location are the same, busted version, while we left the good version behind. The fix for this is to read and copy both sides of the mirror. If the old and new vdevs are mirrors, we will read both sides of the old mirror, and write each copy to the corresponding side of the new mirror. (If the old and new vdevs have a different number of children, we will do this as best as possible.) Even though we aren't verifying checksums, this ensures that as long as there's a good copy of the data, we'll have a good copy after the removal, even if there's silent damage to one side of the mirror. If we're removing a mirror that has some silent damage, we'll have exactly the same damage in the new location (assuming that the new location is also a mirror). 2. When we read from an indirect vdev that points to a mirror vdev, we only consider one copy of the data. This can lead to reduced effective redundancy, because we might read a bad copy of the data from one side of the mirror, and not retry the other, good side of the mirror. Note that the problem is not with the removal process, but rather after the removal has completed (having copied correct data to both sides of the mirror), if one side of the new mirror is silently damaged, we encounter the problem when reading the relocated data via the indirect vdev. Also note that the problem doesn't occur when ZFS knows that one side of the mirror is bad, e.g. when a disk entirely fails or is offlined. The impact is that reads (from indirect vdevs that point to mirrors) may return a checksum error even though the good data exists on one side of the mirror, and scrub doesn't repair all data on the mirror (if some of it is pointed to via an indirect vdev). The fix for this is complicated by "split blocks" - one logical block may be split into two (or more) pieces with each piece moved to a different new location. In this case we need to read all versions of each split (one from each side of the mirror), and figure out which combination of versions results in the correct checksum, and then repair the incorrect versions. This ensures that we supply the same redundancy whether you use device removal or not. For example, if a mirror has small silent errors on all of its children, we can still reconstruct the correct data, as long as those errors are at sufficiently-separated offsets (specifically, separated by the largest block size - default of 128KB, but up to 16MB). Porting notes: * A new indirect vdev check was moved from dsl_scan_needs_resilver_cb() to dsl_scan_needs_resilver(), which was added to ZoL as part of the sequential scrub work. * Passed NULL for zfs_ereport_post_checksum()'s zbookmark_phys_t parameter. The extra parameter is unique to ZoL. * When posting indirect checksum errors the ABD can be passed directly, zfs_ereport_post_checksum() is not yet ABD-aware in OpenZFS. Authored by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Tim Chase <tim@chase2k.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Ported-by: Tim Chase <tim@chase2k.com> OpenZFS-issue: https://illumos.org/issues/9290 OpenZFS-commit: https://github.com/openzfs/openzfs/pull/591 Closes #6900
2018-02-13 22:37:56 +03:00
.sp
.ne 2
.na
Optimize possible split block search space Remove duplicate segment copies to minimize the possible search space for reconstruction. Once reduced an accurate assessment can be made regarding the difficulty in reconstructing the block. Also, ztest will now run zdb with zfs_reconstruct_indirect_combinations_max set to 1000000 in an attempt to avoid checksum errors. Reviewed-by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #6900
2018-03-30 00:50:40 +03:00
\fBzfs_reconstruct_indirect_combinations_max\fR (int)
.ad
.RS 12na
If an indirect split block contains more than this many possible unique
combinations when being reconstructed, consider it too computationally
expensive to check them all. Instead, try at most
\fBzfs_reconstruct_indirect_combinations_max\fR randomly-selected
combinations each time the block is accessed. This allows all segment
copies to participate fairly in the reconstruction when all combinations
cannot be checked and prevents repeated use of one bad copy.
.sp
Refine split block reconstruction Due to a flaw in 4589f3ae the number of unique combinations could be calculated incorrectly. This could result in the random combinations reconstruction being used when it would have been possible to check all combinations. This change fixes the unique combinations calculation and simplifies the reconstruction logic by maintaining a per- segment list of unique copies. The vdev_indirect_splits_damage() function was introduced to validate both the enumeration and random reconstruction logic with ztest. It is implemented such it will never make a known recoverable block unrecoverable. Reviewed-by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #6900 Closes #7934
2018-10-01 20:36:34 +03:00
Default value: \fB256\fR.
OpenZFS 9290 - device removal reduces redundancy of mirrors Mirrors are supposed to provide redundancy in the face of whole-disk failure and silent damage (e.g. some data on disk is not right, but ZFS hasn't detected the whole device as being broken). However, the current device removal implementation bypasses some of the mirror's redundancy. Note that in no case is incorrect data returned, but we might get a checksum error when we should have been able to find the right data. There are two underlying problems: 1. When we remove a mirror device, we only read one side of the mirror. Since we can't verify the checksum, this side may be silently bad, but the good data is on the other side of the mirror (which we didn't read). This can cause the removal to "bake in" the busted data – all copies of the data in the new location are the same, busted version, while we left the good version behind. The fix for this is to read and copy both sides of the mirror. If the old and new vdevs are mirrors, we will read both sides of the old mirror, and write each copy to the corresponding side of the new mirror. (If the old and new vdevs have a different number of children, we will do this as best as possible.) Even though we aren't verifying checksums, this ensures that as long as there's a good copy of the data, we'll have a good copy after the removal, even if there's silent damage to one side of the mirror. If we're removing a mirror that has some silent damage, we'll have exactly the same damage in the new location (assuming that the new location is also a mirror). 2. When we read from an indirect vdev that points to a mirror vdev, we only consider one copy of the data. This can lead to reduced effective redundancy, because we might read a bad copy of the data from one side of the mirror, and not retry the other, good side of the mirror. Note that the problem is not with the removal process, but rather after the removal has completed (having copied correct data to both sides of the mirror), if one side of the new mirror is silently damaged, we encounter the problem when reading the relocated data via the indirect vdev. Also note that the problem doesn't occur when ZFS knows that one side of the mirror is bad, e.g. when a disk entirely fails or is offlined. The impact is that reads (from indirect vdevs that point to mirrors) may return a checksum error even though the good data exists on one side of the mirror, and scrub doesn't repair all data on the mirror (if some of it is pointed to via an indirect vdev). The fix for this is complicated by "split blocks" - one logical block may be split into two (or more) pieces with each piece moved to a different new location. In this case we need to read all versions of each split (one from each side of the mirror), and figure out which combination of versions results in the correct checksum, and then repair the incorrect versions. This ensures that we supply the same redundancy whether you use device removal or not. For example, if a mirror has small silent errors on all of its children, we can still reconstruct the correct data, as long as those errors are at sufficiently-separated offsets (specifically, separated by the largest block size - default of 128KB, but up to 16MB). Porting notes: * A new indirect vdev check was moved from dsl_scan_needs_resilver_cb() to dsl_scan_needs_resilver(), which was added to ZoL as part of the sequential scrub work. * Passed NULL for zfs_ereport_post_checksum()'s zbookmark_phys_t parameter. The extra parameter is unique to ZoL. * When posting indirect checksum errors the ABD can be passed directly, zfs_ereport_post_checksum() is not yet ABD-aware in OpenZFS. Authored by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Tim Chase <tim@chase2k.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Ported-by: Tim Chase <tim@chase2k.com> OpenZFS-issue: https://illumos.org/issues/9290 OpenZFS-commit: https://github.com/openzfs/openzfs/pull/591 Closes #6900
2018-02-13 22:37:56 +03:00
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
.ne 2
.na
\fBzfs_recover\fR (int)
.ad
.RS 12n
Set to attempt to recover from fatal errors. This should only be used as a
last resort, as it typically results in leaked space, or worse.
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
.sp
.ne 2
.na
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 04:27:01 +03:00
\fBzfs_resilver_min_time_ms\fR (int)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.ad
.RS 12n
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 04:27:01 +03:00
Resilvers are processed by the sync thread. While resilvering it will spend
at least this much time working on a resilver between txg flushes.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 04:27:01 +03:00
Default value: \fB3,000\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.RE
Add zfs_scan_ignore_errors tunable When it's set, a DTL range will be cleared even if its scan/scrub had errors. This allows to work around resilver/scrub upon import when the pool has errors. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Tim Chase <tim@chase2k.com> Closes #7293
2018-03-13 20:43:14 +03:00
.sp
.ne 2
.na
\fBzfs_scan_ignore_errors\fR (int)
.ad
.RS 12n
If set to a nonzero value, remove the DTL (dirty time list) upon
completion of a pool scan (scrub) even if there were unrepairable
errors. It is intended to be used during pool repair or recovery to
stop resilvering when the pool is next imported.
.sp
Default value: \fB0\fR.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
.ne 2
.na
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 04:27:01 +03:00
\fBzfs_scrub_min_time_ms\fR (int)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.ad
.RS 12n
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 04:27:01 +03:00
Scrubs are processed by the sync thread. While scrubbing it will spend
at least this much time working on a scrub between txg flushes.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 04:27:01 +03:00
Default value: \fB1,000\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.RE
.sp
.ne 2
.na
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 04:27:01 +03:00
\fBzfs_scan_checkpoint_intval\fR (int)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.ad
.RS 12n
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 04:27:01 +03:00
To preserve progress across reboots the sequential scan algorithm periodically
needs to stop metadata scanning and issue all the verifications I/Os to disk.
The frequency of this flushing is determined by the
Fix duplicate "fB" typo Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <guss80@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: bunder2015 <omfgbunder@gmail.com> Signed-off-by: ajs124 <git@ajs124.de> Closes #7649
2018-06-25 19:50:01 +03:00
\fBzfs_scan_checkpoint_intval\fR tunable.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 04:27:01 +03:00
Default value: \fB7200\fR seconds (every 2 hours).
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.RE
.sp
.ne 2
.na
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 04:27:01 +03:00
\fBzfs_scan_fill_weight\fR (int)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.ad
.RS 12n
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 04:27:01 +03:00
This tunable affects how scrub and resilver I/O segments are ordered. A higher
number indicates that we care more about how filled in a segment is, while a
lower number indicates we care more about the size of the extent without
considering the gaps within a segment. This value is only tunable upon module
insertion. Changing the value afterwards will have no affect on scrub or
resilver performance.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 04:27:01 +03:00
Default value: \fB3\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.RE
.sp
.ne 2
.na
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 04:27:01 +03:00
\fBzfs_scan_issue_strategy\fR (int)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.ad
.RS 12n
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 04:27:01 +03:00
Determines the order that data will be verified while scrubbing or resilvering.
If set to \fB1\fR, data will be verified as sequentially as possible, given the
amount of memory reserved for scrubbing (see \fBzfs_scan_mem_lim_fact\fR). This
may improve scrub performance if the pool's data is very fragmented. If set to
\fB2\fR, the largest mostly-contiguous chunk of found data will be verified
first. By deferring scrubbing of small segments, we may later find adjacent data
to coalesce and increase the segment size. If set to \fB0\fR, zfs will use
strategy \fB1\fR during normal verification and strategy \fB2\fR while taking a
checkpoint.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Sequential scrub and resilvers Currently, scrubs and resilvers can take an extremely long time to complete. This is largely due to the fact that zfs scans process pools in logical order, as determined by each block's bookmark. This makes sense from a simplicity perspective, but blocks in zfs are often scattered randomly across disks, particularly due to zfs's copy-on-write mechanisms. This patch improves performance by splitting scrubs and resilvers into a metadata scanning phase and an IO issuing phase. The metadata scan reads through the structure of the pool and gathers an in-memory queue of I/Os, sorted by size and offset on disk. The issuing phase will then issue the scrub I/Os as sequentially as possible, greatly improving performance. This patch also updates and cleans up some of the scan code which has not been updated in several years. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Authored-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Authored-by: Alek Pinchuk <apinchuk@datto.com> Authored-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #3625 Closes #6256
2017-11-16 04:27:01 +03:00
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
\fBzfs_scan_legacy\fR (int)
.ad
.RS 12n
A value of 0 indicates that scrubs and resilvers will gather metadata in
memory before issuing sequential I/O. A value of 1 indicates that the legacy
algorithm will be used where I/O is initiated as soon as it is discovered.
Changing this value to 0 will not affect scrubs or resilvers that are already
in progress.
.sp
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
\fBzfs_scan_max_ext_gap\fR (int)
.ad
.RS 12n
Indicates the largest gap in bytes between scrub / resilver I/Os that will still
be considered sequential for sorting purposes. Changing this value will not
affect scrubs or resilvers that are already in progress.
.sp
Default value: \fB2097152 (2 MB)\fR.
.RE
.sp
.ne 2
.na
\fBzfs_scan_mem_lim_fact\fR (int)
.ad
.RS 12n
Maximum fraction of RAM used for I/O sorting by sequential scan algorithm.
This tunable determines the hard limit for I/O sorting memory usage.
When the hard limit is reached we stop scanning metadata and start issuing
data verification I/O. This is done until we get below the soft limit.
.sp
Default value: \fB20\fR which is 5% of RAM (1/20).
.RE
.sp
.ne 2
.na
\fBzfs_scan_mem_lim_soft_fact\fR (int)
.ad
.RS 12n
The fraction of the hard limit used to determined the soft limit for I/O sorting
by the sequential scan algorithm. When we cross this limit from bellow no action
is taken. When we cross this limit from above it is because we are issuing
verification I/O. In this case (unless the metadata scan is done) we stop
issuing verification I/O and start scanning metadata again until we get to the
hard limit.
.sp
Default value: \fB20\fR which is 5% of the hard limit (1/20).
.RE
.sp
.ne 2
.na
\fBzfs_scan_vdev_limit\fR (int)
.ad
.RS 12n
Maximum amount of data that can be concurrently issued at once for scrubs and
resilvers per leaf device, given in bytes.
.sp
Default value: \fB41943040\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.RE
Add zfs_send_corrupt_data module option Tuning setting to ignore read/checksum errors when sending data. Signed-off-by: Turbo Fredriksson <turbo@bayour.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1982 Issue #1897
2013-12-18 01:53:52 +04:00
.sp
.ne 2
.na
\fBzfs_send_corrupt_data\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Allow sending of corrupt data (ignore read/checksum errors when sending data)
Add zfs_send_corrupt_data module option Tuning setting to ignore read/checksum errors when sending data. Signed-off-by: Turbo Fredriksson <turbo@bayour.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1982 Issue #1897
2013-12-18 01:53:52 +04:00
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
Fix 'zfs send/recv' hang with 16M blocks When using 16MB blocks the send/recv queue's aren't quite big enough. This change leaves the default 16M queue size which a good value for most pools. But it additionally ensures that the queue sizes are at least twice the allowed zfs_max_recordsize. Reviewed-by: loli10K <ezomori.nozomu@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #7365 Closes #7404
2018-04-09 05:41:15 +03:00
.sp
.ne 2
.na
\fBzfs_send_queue_length\fR (int)
.ad
.RS 12n
The maximum number of bytes allowed in the \fBzfs send\fR queue. This value
must be at least twice the maximum block size in use.
.sp
Default value: \fB16,777,216\fR.
.RE
.sp
.ne 2
.na
\fBzfs_recv_queue_length\fR (int)
.ad
.RS 12n
.sp
The maximum number of bytes allowed in the \fBzfs receive\fR queue. This value
must be at least twice the maximum block size in use.
.sp
Default value: \fB16,777,216\fR.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
.ne 2
.na
\fBzfs_sync_pass_deferred_free\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Flushing of data to disk is done in passes. Defer frees starting in this pass
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Default value: \fB2\fR.
.RE
OpenZFS 9166 - zfs storage pool checkpoint Details about the motivation of this feature and its usage can be found in this blogpost: https://sdimitro.github.io/post/zpool-checkpoint/ A lightning talk of this feature can be found here: https://www.youtube.com/watch?v=fPQA8K40jAM Implementation details can be found in big block comment of spa_checkpoint.c Side-changes that are relevant to this commit but not explained elsewhere: * renames members of "struct metaslab trees to be shorter without losing meaning * space_map_{alloc,truncate}() accept a block size as a parameter. The reason is that in the current state all space maps that we allocate through the DMU use a global tunable (space_map_blksz) which defauls to 4KB. This is ok for metaslab space maps in terms of bandwirdth since they are scattered all over the disk. But for other space maps this default is probably not what we want. Examples are device removal's vdev_obsolete_sm or vdev_chedkpoint_sm from this review. Both of these have a 1:1 relationship with each vdev and could benefit from a bigger block size. Porting notes: * The part of dsl_scan_sync() which handles async destroys has been moved into the new dsl_process_async_destroys() function. * Remove "VERIFY(!(flags & FWRITE))" in "kernel.c" so zhack can write to block device backed pools. * ZTS: * Fix get_txg() in zpool_sync_001_pos due to "checkpoint_txg". * Don't use large dd block sizes on /dev/urandom under Linux in checkpoint_capacity. * Adopt Delphix-OS's setting of 4 (spa_asize_inflation = SPA_DVAS_PER_BP + 1) for the checkpoint_capacity test to speed its attempts to fill the pool * Create the base and nested pools with sync=disabled to speed up the "setup" phase. * Clear labels in test pool between checkpoint tests to avoid duplicate pool issues. * The import_rewind_device_replaced test has been marked as "known to fail" for the reasons listed in its DISCLAIMER. * New module parameters: zfs_spa_discard_memory_limit, zfs_remove_max_bytes_pause (not documented - debugging only) vdev_max_ms_count (formerly metaslabs_per_vdev) vdev_min_ms_count Authored by: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: John Kennedy <john.kennedy@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Richard Lowe <richlowe@richlowe.net> Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Tim Chase <tim@chase2k.com> OpenZFS-issue: https://illumos.org/issues/9166 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/7159fdb8 Closes #7570
2016-12-17 01:11:29 +03:00
.sp
.ne 2
.na
\fBzfs_spa_discard_memory_limit\fR (int)
.ad
.RS 12n
Maximum memory used for prefetching a checkpoint's space map on each
vdev while discarding the checkpoint.
.sp
Default value: \fB16,777,216\fR.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
.ne 2
.na
\fBzfs_sync_pass_dont_compress\fR (int)
.ad
.RS 12n
Don't compress starting in this pass
.sp
Default value: \fB5\fR.
.RE
.sp
.ne 2
.na
\fBzfs_sync_pass_rewrite\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Rewrite new block pointers starting in this pass
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Default value: \fB2\fR.
.RE
OpenZFS 8558, 8602 - lwp_create() returns EAGAIN 8558 lwp_create() returns EAGAIN on system with more than 80K ZFS filesystems On a system with more than 80K ZFS filesystems, we've seen cases where lwp_create() will start to fail by returning EAGAIN. The problem being, for each of those 80K ZFS filesystems, a taskq will be created for each dataset as part of the ZIL for each dataset. Porting Notes: - The new nomem taskq kstat was dropped. - Added module options and documentation for new tunings zfs_zil_clean_taskq_nthr_pct, zfs_zil_clean_taskq_minalloc, zfs_zil_clean_taskq_maxalloc, and zfs_sync_taskq_batch_pct. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Sebastien Roy <sebastien.roy@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> Authored by: Prakash Surya <prakash.surya@delphix.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Chris Dunlop <chris@onthe.net.au> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/8558 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/216d772 8602 remove unused "dp_early_sync_tasks" field from "dsl_pool" structure Reviewed by: Serapheim Dimitropoulos <serapheim@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> Authored by: Prakash Surya <prakash.surya@delphix.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Chris Dunlop <chris@onthe.net.au> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/8602 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/2bcb545 Closes #6779
2017-10-26 22:57:53 +03:00
.sp
.ne 2
.na
\fBzfs_sync_taskq_batch_pct\fR (int)
.ad
.RS 12n
This controls the number of threads used by the dp_sync_taskq. The default
value of 75% will create a maximum of one thread per cpu.
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 22:51:11 +03:00
Default value: \fB75\fR%.
OpenZFS 8558, 8602 - lwp_create() returns EAGAIN 8558 lwp_create() returns EAGAIN on system with more than 80K ZFS filesystems On a system with more than 80K ZFS filesystems, we've seen cases where lwp_create() will start to fail by returning EAGAIN. The problem being, for each of those 80K ZFS filesystems, a taskq will be created for each dataset as part of the ZIL for each dataset. Porting Notes: - The new nomem taskq kstat was dropped. - Added module options and documentation for new tunings zfs_zil_clean_taskq_nthr_pct, zfs_zil_clean_taskq_minalloc, zfs_zil_clean_taskq_maxalloc, and zfs_sync_taskq_batch_pct. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Sebastien Roy <sebastien.roy@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> Authored by: Prakash Surya <prakash.surya@delphix.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Chris Dunlop <chris@onthe.net.au> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/8558 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/216d772 8602 remove unused "dp_early_sync_tasks" field from "dsl_pool" structure Reviewed by: Serapheim Dimitropoulos <serapheim@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> Authored by: Prakash Surya <prakash.surya@delphix.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Chris Dunlop <chris@onthe.net.au> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/8602 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/2bcb545 Closes #6779
2017-10-26 22:57:53 +03:00
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
.ne 2
.na
\fBzfs_txg_history\fR (int)
.ad
.RS 12n
Multi-modifier protection (MMP) Add multihost=on|off pool property to control MMP. When enabled a new thread writes uberblocks to the last slot in each label, at a set frequency, to indicate to other hosts the pool is actively imported. These uberblocks are the last synced uberblock with an updated timestamp. Property defaults to off. During tryimport, find the "best" uberblock (newest txg and timestamp) repeatedly, checking for change in the found uberblock. Include the results of the activity test in the config returned by tryimport. These results are reported to user in "zpool import". Allow the user to control the period between MMP writes, and the duration of the activity test on import, via a new module parameter zfs_multihost_interval. The period is specified in milliseconds. The activity test duration is calculated from this value, and from the mmp_delay in the "best" uberblock found initially. Add a kstat interface to export statistics about Multiple Modifier Protection (MMP) updates. Include the last synced txg number, the timestamp, the delay since the last MMP update, the VDEV GUID, the VDEV label that received the last MMP update, and the VDEV path. Abbreviated output below. $ cat /proc/spl/kstat/zfs/mypool/multihost 31 0 0x01 10 880 105092382393521 105144180101111 txg timestamp mmp_delay vdev_guid vdev_label vdev_path 20468 261337 250274925 68396651780 3 /dev/sda 20468 261339 252023374 6267402363293 1 /dev/sdc 20468 261340 252000858 6698080955233 1 /dev/sdx 20468 261341 251980635 783892869810 2 /dev/sdy 20468 261342 253385953 8923255792467 3 /dev/sdd 20468 261344 253336622 042125143176 0 /dev/sdab 20468 261345 253310522 1200778101278 2 /dev/sde 20468 261346 253286429 0950576198362 2 /dev/sdt 20468 261347 253261545 96209817917 3 /dev/sds 20468 261349 253238188 8555725937673 3 /dev/sdb Add a new tunable zfs_multihost_history to specify the number of MMP updates to store history for. By default it is set to zero meaning that no MMP statistics are stored. When using ztest to generate activity, for automated tests of the MMP function, some test functions interfere with the test. For example, the pool is exported to run zdb and then imported again. Add a new ztest function, "-M", to alter ztest behavior to prevent this. Add new tests to verify the new functionality. Tests provided by Giuseppe Di Natale. Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Reviewed-by: Ned Bass <bass6@llnl.gov> Reviewed-by: Andreas Dilger <andreas.dilger@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Olaf Faaland <faaland1@llnl.gov> Closes #745 Closes #6279
2017-07-08 06:20:35 +03:00
Historical statistics for the last N txgs will be available in
\fB/proc/spl/kstat/zfs/<pool>/txgs\fR
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 23:15:10 +03:00
Default value: \fB0\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.RE
.sp
.ne 2
.na
\fBzfs_txg_timeout\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Flush dirty data to disk at least every N seconds (maximum txg duration)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Default value: \fB5\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_aggregation_limit\fR (int)
.ad
.RS 12n
Max vdev I/O aggregation size
.sp
Default value: \fB131,072\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_cache_bshift\fR (int)
.ad
.RS 12n
Shift size to inflate reads too
.sp
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Default value: \fB16\fR (effectively 65536).
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.RE
.sp
.ne 2
.na
\fBzfs_vdev_cache_max\fR (int)
.ad
.RS 12n
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 23:15:10 +03:00
Inflate reads smaller than this value to meet the \fBzfs_vdev_cache_bshift\fR
size (default 64k).
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
.sp
Default value: \fB16384\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.RE
.sp
.ne 2
.na
\fBzfs_vdev_cache_size\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Total size of the per-disk cache in bytes.
.sp
Currently this feature is disabled as it has been found to not be helpful
for performance and in some cases harmful.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
FreeBSD r256956: Improve ZFS N-way mirror read performance by using load and locality information. The existing algorithm selects a preferred leaf vdev based on offset of the zio request modulo the number of members in the mirror. It assumes the devices are of equal performance and that spreading the requests randomly over both drives will be sufficient to saturate them. In practice this results in the leaf vdevs being under utilized. The new algorithm takes into the following additional factors: * Load of the vdevs (number outstanding I/O requests) * The locality of last queued I/O vs the new I/O request. Within the locality calculation additional knowledge about the underlying vdev is considered such as; is the device backing the vdev a rotating media device. This results in performance increases across the board as well as significant increases for predominantly streaming loads and for configurations which don't have evenly performing devices. The following are results from a setup with 3 Way Mirror with 2 x HD's and 1 x SSD from a basic test running multiple parrallel dd's. With pre-fetch disabled (vfs.zfs.prefetch_disable=1): == Stripe Balanced (default) == Read 15360MB using bs: 1048576, readers: 3, took 161 seconds @ 95 MB/s == Load Balanced (zfslinux) == Read 15360MB using bs: 1048576, readers: 3, took 297 seconds @ 51 MB/s == Load Balanced (locality freebsd) == Read 15360MB using bs: 1048576, readers: 3, took 54 seconds @ 284 MB/s With pre-fetch enabled (vfs.zfs.prefetch_disable=0): == Stripe Balanced (default) == Read 15360MB using bs: 1048576, readers: 3, took 91 seconds @ 168 MB/s == Load Balanced (zfslinux) == Read 15360MB using bs: 1048576, readers: 3, took 108 seconds @ 142 MB/s == Load Balanced (locality freebsd) == Read 15360MB using bs: 1048576, readers: 3, took 48 seconds @ 320 MB/s In addition to the performance changes the code was also restructured, with the help of Justin Gibbs, to provide a more logical flow which also ensures vdevs loads are only calculated from the set of valid candidates. The following additional sysctls where added to allow the administrator to tune the behaviour of the load algorithm: * vfs.zfs.vdev.mirror.rotating_inc * vfs.zfs.vdev.mirror.rotating_seek_inc * vfs.zfs.vdev.mirror.rotating_seek_offset * vfs.zfs.vdev.mirror.non_rotating_inc * vfs.zfs.vdev.mirror.non_rotating_seek_inc These changes where based on work started by the zfsonlinux developers: https://github.com/zfsonlinux/zfs/pull/1487 Reviewed by: gibbs, mav, will MFC after: 2 weeks Sponsored by: Multiplay References: https://github.com/freebsd/freebsd@5c7a6f5d https://github.com/freebsd/freebsd@31b7f68d https://github.com/freebsd/freebsd@e186f564 Performance Testing: https://github.com/zfsonlinux/zfs/pull/4334#issuecomment-189057141 Porting notes: - The tunables were adjusted to have ZoL-style names. - The code was modified to use ZoL's vd_nonrot. - Fixes were done to make cstyle.pl happy - Merge conflicts were handled manually - freebsd/freebsd@e186f564bc946f82c76e0b34c2f0370ed9aea022 by my collegue Andriy Gapon has been included. It applied perfectly, but added a cstyle regression. - This replaces 556011dbec2d10579819078559a77630fc559112 entirely. - A typo "IO'a" has been corrected to say "IO's" - Descriptions of new tunables were added to man/man5/zfs-module-parameters.5. Ported-by: Richard Yao <ryao@gentoo.org> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4334
2016-02-13 04:47:22 +03:00
\fBzfs_vdev_mirror_rotating_inc\fR (int)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.ad
.RS 12n
FreeBSD r256956: Improve ZFS N-way mirror read performance by using load and locality information. The existing algorithm selects a preferred leaf vdev based on offset of the zio request modulo the number of members in the mirror. It assumes the devices are of equal performance and that spreading the requests randomly over both drives will be sufficient to saturate them. In practice this results in the leaf vdevs being under utilized. The new algorithm takes into the following additional factors: * Load of the vdevs (number outstanding I/O requests) * The locality of last queued I/O vs the new I/O request. Within the locality calculation additional knowledge about the underlying vdev is considered such as; is the device backing the vdev a rotating media device. This results in performance increases across the board as well as significant increases for predominantly streaming loads and for configurations which don't have evenly performing devices. The following are results from a setup with 3 Way Mirror with 2 x HD's and 1 x SSD from a basic test running multiple parrallel dd's. With pre-fetch disabled (vfs.zfs.prefetch_disable=1): == Stripe Balanced (default) == Read 15360MB using bs: 1048576, readers: 3, took 161 seconds @ 95 MB/s == Load Balanced (zfslinux) == Read 15360MB using bs: 1048576, readers: 3, took 297 seconds @ 51 MB/s == Load Balanced (locality freebsd) == Read 15360MB using bs: 1048576, readers: 3, took 54 seconds @ 284 MB/s With pre-fetch enabled (vfs.zfs.prefetch_disable=0): == Stripe Balanced (default) == Read 15360MB using bs: 1048576, readers: 3, took 91 seconds @ 168 MB/s == Load Balanced (zfslinux) == Read 15360MB using bs: 1048576, readers: 3, took 108 seconds @ 142 MB/s == Load Balanced (locality freebsd) == Read 15360MB using bs: 1048576, readers: 3, took 48 seconds @ 320 MB/s In addition to the performance changes the code was also restructured, with the help of Justin Gibbs, to provide a more logical flow which also ensures vdevs loads are only calculated from the set of valid candidates. The following additional sysctls where added to allow the administrator to tune the behaviour of the load algorithm: * vfs.zfs.vdev.mirror.rotating_inc * vfs.zfs.vdev.mirror.rotating_seek_inc * vfs.zfs.vdev.mirror.rotating_seek_offset * vfs.zfs.vdev.mirror.non_rotating_inc * vfs.zfs.vdev.mirror.non_rotating_seek_inc These changes where based on work started by the zfsonlinux developers: https://github.com/zfsonlinux/zfs/pull/1487 Reviewed by: gibbs, mav, will MFC after: 2 weeks Sponsored by: Multiplay References: https://github.com/freebsd/freebsd@5c7a6f5d https://github.com/freebsd/freebsd@31b7f68d https://github.com/freebsd/freebsd@e186f564 Performance Testing: https://github.com/zfsonlinux/zfs/pull/4334#issuecomment-189057141 Porting notes: - The tunables were adjusted to have ZoL-style names. - The code was modified to use ZoL's vd_nonrot. - Fixes were done to make cstyle.pl happy - Merge conflicts were handled manually - freebsd/freebsd@e186f564bc946f82c76e0b34c2f0370ed9aea022 by my collegue Andriy Gapon has been included. It applied perfectly, but added a cstyle regression. - This replaces 556011dbec2d10579819078559a77630fc559112 entirely. - A typo "IO'a" has been corrected to say "IO's" - Descriptions of new tunables were added to man/man5/zfs-module-parameters.5. Ported-by: Richard Yao <ryao@gentoo.org> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4334
2016-02-13 04:47:22 +03:00
A number by which the balancing algorithm increments the load calculation for
the purpose of selecting the least busy mirror member when an I/O immediately
follows its predecessor on rotational vdevs for the purpose of making decisions
based on load.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
FreeBSD r256956: Improve ZFS N-way mirror read performance by using load and locality information. The existing algorithm selects a preferred leaf vdev based on offset of the zio request modulo the number of members in the mirror. It assumes the devices are of equal performance and that spreading the requests randomly over both drives will be sufficient to saturate them. In practice this results in the leaf vdevs being under utilized. The new algorithm takes into the following additional factors: * Load of the vdevs (number outstanding I/O requests) * The locality of last queued I/O vs the new I/O request. Within the locality calculation additional knowledge about the underlying vdev is considered such as; is the device backing the vdev a rotating media device. This results in performance increases across the board as well as significant increases for predominantly streaming loads and for configurations which don't have evenly performing devices. The following are results from a setup with 3 Way Mirror with 2 x HD's and 1 x SSD from a basic test running multiple parrallel dd's. With pre-fetch disabled (vfs.zfs.prefetch_disable=1): == Stripe Balanced (default) == Read 15360MB using bs: 1048576, readers: 3, took 161 seconds @ 95 MB/s == Load Balanced (zfslinux) == Read 15360MB using bs: 1048576, readers: 3, took 297 seconds @ 51 MB/s == Load Balanced (locality freebsd) == Read 15360MB using bs: 1048576, readers: 3, took 54 seconds @ 284 MB/s With pre-fetch enabled (vfs.zfs.prefetch_disable=0): == Stripe Balanced (default) == Read 15360MB using bs: 1048576, readers: 3, took 91 seconds @ 168 MB/s == Load Balanced (zfslinux) == Read 15360MB using bs: 1048576, readers: 3, took 108 seconds @ 142 MB/s == Load Balanced (locality freebsd) == Read 15360MB using bs: 1048576, readers: 3, took 48 seconds @ 320 MB/s In addition to the performance changes the code was also restructured, with the help of Justin Gibbs, to provide a more logical flow which also ensures vdevs loads are only calculated from the set of valid candidates. The following additional sysctls where added to allow the administrator to tune the behaviour of the load algorithm: * vfs.zfs.vdev.mirror.rotating_inc * vfs.zfs.vdev.mirror.rotating_seek_inc * vfs.zfs.vdev.mirror.rotating_seek_offset * vfs.zfs.vdev.mirror.non_rotating_inc * vfs.zfs.vdev.mirror.non_rotating_seek_inc These changes where based on work started by the zfsonlinux developers: https://github.com/zfsonlinux/zfs/pull/1487 Reviewed by: gibbs, mav, will MFC after: 2 weeks Sponsored by: Multiplay References: https://github.com/freebsd/freebsd@5c7a6f5d https://github.com/freebsd/freebsd@31b7f68d https://github.com/freebsd/freebsd@e186f564 Performance Testing: https://github.com/zfsonlinux/zfs/pull/4334#issuecomment-189057141 Porting notes: - The tunables were adjusted to have ZoL-style names. - The code was modified to use ZoL's vd_nonrot. - Fixes were done to make cstyle.pl happy - Merge conflicts were handled manually - freebsd/freebsd@e186f564bc946f82c76e0b34c2f0370ed9aea022 by my collegue Andriy Gapon has been included. It applied perfectly, but added a cstyle regression. - This replaces 556011dbec2d10579819078559a77630fc559112 entirely. - A typo "IO'a" has been corrected to say "IO's" - Descriptions of new tunables were added to man/man5/zfs-module-parameters.5. Ported-by: Richard Yao <ryao@gentoo.org> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4334
2016-02-13 04:47:22 +03:00
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_mirror_rotating_seek_inc\fR (int)
.ad
.RS 12n
A number by which the balancing algorithm increments the load calculation for
the purpose of selecting the least busy mirror member when an I/O lacks
locality as defined by the zfs_vdev_mirror_rotating_seek_offset. I/Os within
this that are not immediately following the previous I/O are incremented by
half.
.sp
Default value: \fB5\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_mirror_rotating_seek_offset\fR (int)
.ad
.RS 12n
The maximum distance for the last queued I/O in which the balancing algorithm
considers an I/O to have locality.
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB1048576\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_mirror_non_rotating_inc\fR (int)
.ad
.RS 12n
A number by which the balancing algorithm increments the load calculation for
the purpose of selecting the least busy mirror member on non-rotational vdevs
when I/Os do not immediately follow one another.
.sp
Default value: \fB0\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_mirror_non_rotating_seek_inc\fR (int)
.ad
.RS 12n
A number by which the balancing algorithm increments the load calculation for
the purpose of selecting the least busy mirror member when an I/O lacks
locality as defined by the zfs_vdev_mirror_rotating_seek_offset. I/Os within
this that are not immediately following the previous I/O are incremented by
half.
.sp
Default value: \fB1\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.RE
.sp
.ne 2
.na
\fBzfs_vdev_read_gap_limit\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Aggregate read I/O operations if the gap on-disk between them is within this
threshold.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Default value: \fB32,768\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_scheduler\fR (charp)
.ad
.RS 12n
Update zfs module parameters man5 Update zfs module parameters man5 with missing parameter details for multiple tunings. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Signed-off-by: Alex Braunegg <alex.braunegg@gmail.com> Closes #6785
2017-10-30 23:15:10 +03:00
Set the Linux I/O scheduler on whole disk vdevs to this scheduler. Valid options
are noop, cfq, bfq & deadline
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Default value: \fBnoop\fR.
.RE
.sp
.ne 2
.na
\fBzfs_vdev_write_gap_limit\fR (int)
.ad
.RS 12n
Aggregate write I/O over gap
.sp
Default value: \fB4,096\fR.
.RE
SIMD implementation of vdev_raidz generate and reconstruct routines This is a new implementation of RAIDZ1/2/3 routines using x86_64 scalar, SSE, and AVX2 instruction sets. Included are 3 parity generation routines (P, PQ, and PQR) and 7 reconstruction routines, for all RAIDZ level. On module load, a quick benchmark of supported routines will select the fastest for each operation and they will be used at runtime. Original implementation is still present and can be selected via module parameter. Patch contains: - specialized gen/rec routines for all RAIDZ levels, - new scalar raidz implementation (unrolled), - two x86_64 SIMD implementations (SSE and AVX2 instructions sets), - fastest routines selected on module load (benchmark). - cmd/raidz_test - verify and benchmark all implementations - added raidz_test to the ZFS Test Suite New zfs module parameters: - zfs_vdev_raidz_impl (str): selects the implementation to use. On module load, the parameter will only accept first 3 options, and the other implementations can be set once module is finished loading. Possible values for this option are: "fastest" - use the fastest math available "original" - use the original raidz code "scalar" - new scalar impl "sse" - new SSE impl if available "avx2" - new AVX2 impl if available See contents of `/sys/module/zfs/parameters/zfs_vdev_raidz_impl` to get the list of supported values. If an implementation is not supported on the system, it will not be shown. Currently selected option is enclosed in `[]`. Signed-off-by: Gvozden Neskovic <neskovic@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4328
2016-04-25 11:04:31 +03:00
.sp
.ne 2
.na
\fBzfs_vdev_raidz_impl\fR (string)
.ad
.RS 12n
Fixes and enhancements of SIMD raidz parity - Implementation lock replaced with atomic variable - Trailing whitespace is removed from user specified parameter, to enhance experience when using commands that add newline, e.g. `echo` - raidz_test: remove dependency on `getrusage()` and RUSAGE_THREAD, Issue #4813 - silence `cppcheck` in vdev_raidz, partial solution of Issue #1392 - Minor fixes and cleanups - Enable use of original parity methods in [fastest] configuration. New opaque original ops structure, representing native methods, is added to supported raidz methods. Original parity methods are executed if selected implementation has NULL fn pointer. Signed-off-by: Gvozden Neskovic <neskovic@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #4813 Issue #1392
2016-07-17 20:41:11 +03:00
Parameter for selecting raidz parity implementation to use.
SIMD implementation of vdev_raidz generate and reconstruct routines This is a new implementation of RAIDZ1/2/3 routines using x86_64 scalar, SSE, and AVX2 instruction sets. Included are 3 parity generation routines (P, PQ, and PQR) and 7 reconstruction routines, for all RAIDZ level. On module load, a quick benchmark of supported routines will select the fastest for each operation and they will be used at runtime. Original implementation is still present and can be selected via module parameter. Patch contains: - specialized gen/rec routines for all RAIDZ levels, - new scalar raidz implementation (unrolled), - two x86_64 SIMD implementations (SSE and AVX2 instructions sets), - fastest routines selected on module load (benchmark). - cmd/raidz_test - verify and benchmark all implementations - added raidz_test to the ZFS Test Suite New zfs module parameters: - zfs_vdev_raidz_impl (str): selects the implementation to use. On module load, the parameter will only accept first 3 options, and the other implementations can be set once module is finished loading. Possible values for this option are: "fastest" - use the fastest math available "original" - use the original raidz code "scalar" - new scalar impl "sse" - new SSE impl if available "avx2" - new AVX2 impl if available See contents of `/sys/module/zfs/parameters/zfs_vdev_raidz_impl` to get the list of supported values. If an implementation is not supported on the system, it will not be shown. Currently selected option is enclosed in `[]`. Signed-off-by: Gvozden Neskovic <neskovic@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4328
2016-04-25 11:04:31 +03:00
Options marked (always) below may be selected on module load as they are
supported on all systems.
The remaining options may only be set after the module is loaded, as they
are available only if the implementations are compiled in and supported
on the running system.
Once the module is loaded, the content of
/sys/module/zfs/parameters/zfs_vdev_raidz_impl will show available options
with the currently selected one enclosed in [].
Possible options are:
fastest - (always) implementation selected using built-in benchmark
original - (always) original raidz implementation
scalar - (always) scalar raidz implementation
Add RAID-Z routines for SSE2 instruction set, in x86_64 mode. The patch covers low-end and older x86 CPUs. Parity generation is equivalent to SSSE3 implementation, but reconstruction is somewhat slower. Previous 'sse' implementation is renamed to 'ssse3' to indicate highest instruction set used. Benchmark results: scalar_rec_p 4 720476442 scalar_rec_q 4 187462804 scalar_rec_r 4 138996096 scalar_rec_pq 4 140834951 scalar_rec_pr 4 129332035 scalar_rec_qr 4 81619194 scalar_rec_pqr 4 53376668 sse2_rec_p 4 2427757064 sse2_rec_q 4 747120861 sse2_rec_r 4 499871637 sse2_rec_pq 4 522403710 sse2_rec_pr 4 464632780 sse2_rec_qr 4 319124434 sse2_rec_pqr 4 205794190 ssse3_rec_p 4 2519939444 ssse3_rec_q 4 1003019289 ssse3_rec_r 4 616428767 ssse3_rec_pq 4 706326396 ssse3_rec_pr 4 570493618 ssse3_rec_qr 4 400185250 ssse3_rec_pqr 4 377541245 original_rec_p 4 691658568 original_rec_q 4 195510948 original_rec_r 4 26075538 original_rec_pq 4 103087368 original_rec_pr 4 15767058 original_rec_qr 4 15513175 original_rec_pqr 4 10746357 Signed-off-by: Gvozden Neskovic <neskovic@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4783
2016-06-28 20:49:53 +03:00
sse2 - implementation using SSE2 instruction set (64bit x86 only)
ssse3 - implementation using SSSE3 instruction set (64bit x86 only)
SIMD implementation of vdev_raidz generate and reconstruct routines This is a new implementation of RAIDZ1/2/3 routines using x86_64 scalar, SSE, and AVX2 instruction sets. Included are 3 parity generation routines (P, PQ, and PQR) and 7 reconstruction routines, for all RAIDZ level. On module load, a quick benchmark of supported routines will select the fastest for each operation and they will be used at runtime. Original implementation is still present and can be selected via module parameter. Patch contains: - specialized gen/rec routines for all RAIDZ levels, - new scalar raidz implementation (unrolled), - two x86_64 SIMD implementations (SSE and AVX2 instructions sets), - fastest routines selected on module load (benchmark). - cmd/raidz_test - verify and benchmark all implementations - added raidz_test to the ZFS Test Suite New zfs module parameters: - zfs_vdev_raidz_impl (str): selects the implementation to use. On module load, the parameter will only accept first 3 options, and the other implementations can be set once module is finished loading. Possible values for this option are: "fastest" - use the fastest math available "original" - use the original raidz code "scalar" - new scalar impl "sse" - new SSE impl if available "avx2" - new AVX2 impl if available See contents of `/sys/module/zfs/parameters/zfs_vdev_raidz_impl` to get the list of supported values. If an implementation is not supported on the system, it will not be shown. Currently selected option is enclosed in `[]`. Signed-off-by: Gvozden Neskovic <neskovic@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4328
2016-04-25 11:04:31 +03:00
avx2 - implementation using AVX2 instruction set (64bit x86 only)
Add parity generation/rebuild using AVX-512 for x86-64 avx512f should work on all AVX512 hardware, since it only uses Foundation instructions. avx512bw should be faster on hardware supporting the AVW512BW extension. We can use full-width pshufb (instead of relying on the 256 bits AVX2 pshufb). As a side-effect, the code is also unrolled more. Reviewed-by: Richard Laager <rlaager@wiktel.com> Reviewed-by: Gvozden Neskovic <neskovic@gmail.com> Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Romain Dolbeau <romain.github@dolbeau.name> Closes #5219
2016-11-02 22:40:23 +03:00
avx512f - implementation using AVX512F instruction set (64bit x86 only)
avx512bw - implementation using AVX512F & AVX512BW instruction sets (64bit x86 only)
Add parity generation/rebuild using 128-bits NEON for Aarch64 This re-use the framework established for SSE2, SSSE3 and AVX2. However, GCC is using FP registers on Aarch64, so unlike SSE/AVX2 we can't rely on the registers being left alone between ASM statements. So instead, the NEON code uses C variables and GCC extended ASM syntax. Note that since the kernel explicitly disable vector registers, they have to be locally re-enabled explicitly. As we use the variable's number to define the symbolic name, and GCC won't allow duplicate symbolic names, numbers have to be unique. Even when the code is not going to be used (e.g. the case for 4 registers when using the macro with only 2). Only the actually used variables should be declared, otherwise the build will fails in debug mode. This requires the replacement of the XOR(X,X) syntax by a new ZERO(X) macro, which does the same thing but without repeating the argument. And perhaps someday there will be a machine where there is a more efficient way to zero a register than XOR with itself. This affects scalar, SSE2, SSSE3 and AVX2 as they need the new macro. It's possible to write faster implementations (different scheduling, different unrolling, interleaving NEON and scalar, ...) for various cores, but this one has the advantage of fitting in the current state of the code, and thus is likely easier to review/check/merge. The only difference between aarch64-neon and aarch64-neonx2 is that aarch64-neonx2 unroll some functions some more. Reviewed-by: Gvozden Neskovic <neskovic@gmail.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Romain Dolbeau <romain.dolbeau@atos.net> Closes #4801
2016-10-03 19:44:00 +03:00
aarch64_neon - implementation using NEON (Aarch64/64 bit ARMv8 only)
aarch64_neonx2 - implementation using NEON with more unrolling (Aarch64/64 bit ARMv8 only)
SIMD implementation of vdev_raidz generate and reconstruct routines This is a new implementation of RAIDZ1/2/3 routines using x86_64 scalar, SSE, and AVX2 instruction sets. Included are 3 parity generation routines (P, PQ, and PQR) and 7 reconstruction routines, for all RAIDZ level. On module load, a quick benchmark of supported routines will select the fastest for each operation and they will be used at runtime. Original implementation is still present and can be selected via module parameter. Patch contains: - specialized gen/rec routines for all RAIDZ levels, - new scalar raidz implementation (unrolled), - two x86_64 SIMD implementations (SSE and AVX2 instructions sets), - fastest routines selected on module load (benchmark). - cmd/raidz_test - verify and benchmark all implementations - added raidz_test to the ZFS Test Suite New zfs module parameters: - zfs_vdev_raidz_impl (str): selects the implementation to use. On module load, the parameter will only accept first 3 options, and the other implementations can be set once module is finished loading. Possible values for this option are: "fastest" - use the fastest math available "original" - use the original raidz code "scalar" - new scalar impl "sse" - new SSE impl if available "avx2" - new AVX2 impl if available See contents of `/sys/module/zfs/parameters/zfs_vdev_raidz_impl` to get the list of supported values. If an implementation is not supported on the system, it will not be shown. Currently selected option is enclosed in `[]`. Signed-off-by: Gvozden Neskovic <neskovic@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4328
2016-04-25 11:04:31 +03:00
.sp
Default value: \fBfastest\fR.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
.ne 2
.na
\fBzfs_zevent_cols\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
When zevents are logged to the console use this as the word wrap width.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Default value: \fB80\fR.
.RE
.sp
.ne 2
.na
\fBzfs_zevent_console\fR (int)
.ad
.RS 12n
Log events to the console
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
.sp
.ne 2
.na
\fBzfs_zevent_len_max\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Max event queue length. A value of 0 will result in a calculated value which
increases with the number of CPUs in the system (minimum 64 events). Events
in the queue can be viewed with the \fBzpool events\fR command.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Default value: \fB0\fR.
.RE
OpenZFS 8558, 8602 - lwp_create() returns EAGAIN 8558 lwp_create() returns EAGAIN on system with more than 80K ZFS filesystems On a system with more than 80K ZFS filesystems, we've seen cases where lwp_create() will start to fail by returning EAGAIN. The problem being, for each of those 80K ZFS filesystems, a taskq will be created for each dataset as part of the ZIL for each dataset. Porting Notes: - The new nomem taskq kstat was dropped. - Added module options and documentation for new tunings zfs_zil_clean_taskq_nthr_pct, zfs_zil_clean_taskq_minalloc, zfs_zil_clean_taskq_maxalloc, and zfs_sync_taskq_batch_pct. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Sebastien Roy <sebastien.roy@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> Authored by: Prakash Surya <prakash.surya@delphix.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Chris Dunlop <chris@onthe.net.au> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/8558 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/216d772 8602 remove unused "dp_early_sync_tasks" field from "dsl_pool" structure Reviewed by: Serapheim Dimitropoulos <serapheim@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> Authored by: Prakash Surya <prakash.surya@delphix.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Chris Dunlop <chris@onthe.net.au> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/8602 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/2bcb545 Closes #6779
2017-10-26 22:57:53 +03:00
.sp
.ne 2
.na
\fBzfs_zil_clean_taskq_maxalloc\fR (int)
.ad
.RS 12n
The maximum number of taskq entries that are allowed to be cached. When this
OpenZFS 8909 - 8585 can cause a use-after-free kernel panic Authored by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: John Kennedy <jwk404@gmail.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Brad Lewis <brad.lewis@delphix.com> Reviewed by: Igor Kozhukhov <igor@dilos.org> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Robert Mustacchi <rm@joyent.com> Ported-by: Prakash Surya <prakash.surya@delphix.com> PROBLEM ======= There's a race condition that exists if `zil_free_lwb` races with either `zil_commit_waiter_timeout` and/or `zil_lwb_flush_vdevs_done`. Here's an example panic due to this bug: > ::status debugging crash dump vmcore.0 (64-bit) from ip-10-110-205-40 operating system: 5.11 dlpx-5.2.2.0_2017-12-04-17-28-32b6ba51fb (i86pc) image uuid: 4af0edfb-e58e-6ed8-cafc-d3e9167c7513 panic message: BAD TRAP: type=e (#pf Page fault) rp=ffffff0010555970 addr=60 occurred in module "zfs" due to a NULL pointer dereference dump content: kernel pages only > $c zio_shrink+0x12() zil_lwb_write_issue+0x30d(ffffff03dcd15cc0, ffffff03e0730e20) zil_commit_waiter_timeout+0xa2(ffffff03dcd15cc0, ffffff03d97ffcf8) zil_commit_waiter+0xf3(ffffff03dcd15cc0, ffffff03d97ffcf8) zil_commit+0x80(ffffff03dcd15cc0, 9a9) zfs_write+0xc34(ffffff03dc38b140, ffffff0010555e60, 40, ffffff03e00fb758, 0) fop_write+0x5b(ffffff03dc38b140, ffffff0010555e60, 40, ffffff03e00fb758, 0) write+0x250(42, fffffd7ff4832000, 2000) sys_syscall+0x177() If there's an outstanding lwb that's in `zil_commit_waiter_timeout` waiting to timeout, waiting on it's waiter's CV, we must be sure not to call `zil_free_lwb`. If we end up calling `zil_free_lwb`, then that LWB may be freed and can result in a use-after-free situation where the stale lwb pointer stored in the `zil_commit_waiter_t` structure of the thread waiting on the waiter's CV is used. A similar situation can occur if an lwb is issued to disk, and thus in the `LWB_STATE_ISSUED` state, and `zil_free_lwb` is called while the disk is servicing that lwb. In this situation, the lwb will be freed by `zil_free_lwb`, which will result in a use-after-free situation when the lwb's zio completes, and `zil_lwb_flush_vdevs_done` is called. This race condition is prevented in `zil_close` by calling `zil_commit` before `zil_free_lwb` is called, which will ensure all outstanding (i.e. all lwb's in the `LWB_STATE_OPEN` and/or `LWB_STATE_ISSUED` states) reach the `LWB_STATE_DONE` state before the lwb's are freed (`zil_commit` will not return untill all the lwb's are `LWB_STATE_DONE`). Further, this race condition is prevented in `zil_sync` by only calling `zil_free_lwb` for lwb's that do not have their `lwb_buf` pointer set. All lwb's not in the `LWB_STATE_DONE` state will have a non-null value for this pointer; the pointer is only cleared in `zil_lwb_flush_vdevs_done`, at which point the lwb's state will be changed to `LWB_STATE_DONE`. This race *is* present in `zil_suspend`, leading to this bug. At first glance, it would appear as though this would not be true because `zil_suspend` will call `zil_commit`, just like `zil_close`, but the problem is that `zil_suspend` will set the zilog's `zl_suspend` field prior to calling `zil_commit`. Further, in `zil_commit`, if `zl_suspend` is set, `zil_commit` will take a special branch of logic and use `txg_wait_synced` instead of performing the normal `zil_commit` logic. This call to `txg_wait_synced` might be good enough for the data to reach disk safely before it returns, but it does not ensure that all outstanding lwb's reach the `LWB_STATE_DONE` state before it returns. This is because, if there's an lwb "stuck" in `zil_commit_waiter_timeout`, waiting for it's lwb to timeout, it will maintain a non-null value for it's `lwb_buf` field and thus `zil_sync` will not free that lwb. Thus, even though the lwb's data is already on disk, the lwb will be left lingering, waiting on the CV, and will eventually timeout and be issued to disk even though the write is unnecessary. So, after `zil_commit` is called from `zil_suspend`, we incorrectly assume that there are not outstanding lwb's, and proceed to free all lwb's found on the zilog's lwb list. As a result, we free the lwb that will later be used `zil_commit_waiter_timeout`. SOLUTION ======== The solution to this, is to ensure all outstanding lwb's complete before calling `zil_free_lwb` via `zil_destroy` in `zil_suspend`. This patch accomplishes this goal by forcing the normal `zil_commit` logic when called from `zil_sync`. Now, `zil_suspend` will call `zil_commit_impl` which will always use the normal logic of waiting/issuing lwb's to disk before it returns. As a result, any lwb's outstanding when `zil_commit_impl` is called will be guaranteed to reach the `LWB_STATE_DONE` state by the time it returns. Further, no new lwb's will be created via `zil_commit` since the zilog's `zl_suspend` flag will be set. This will force all new callers of `zil_commit` to use `txg_wait_synced` instead of creating and issuing new lwb's. Thus, all lwb's left on the zilog's lwb list when `zil_destroy` is called will be in the `LWB_STATE_DONE` state, and we'll avoid this race condition. OpenZFS-issue: https://www.illumos.org/issues/8909 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/ece62b6f8d Closes #6940
2017-12-07 22:26:32 +03:00
limit is exceeded transaction records (itxs) will be cleaned synchronously.
OpenZFS 8558, 8602 - lwp_create() returns EAGAIN 8558 lwp_create() returns EAGAIN on system with more than 80K ZFS filesystems On a system with more than 80K ZFS filesystems, we've seen cases where lwp_create() will start to fail by returning EAGAIN. The problem being, for each of those 80K ZFS filesystems, a taskq will be created for each dataset as part of the ZIL for each dataset. Porting Notes: - The new nomem taskq kstat was dropped. - Added module options and documentation for new tunings zfs_zil_clean_taskq_nthr_pct, zfs_zil_clean_taskq_minalloc, zfs_zil_clean_taskq_maxalloc, and zfs_sync_taskq_batch_pct. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Sebastien Roy <sebastien.roy@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> Authored by: Prakash Surya <prakash.surya@delphix.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Chris Dunlop <chris@onthe.net.au> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/8558 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/216d772 8602 remove unused "dp_early_sync_tasks" field from "dsl_pool" structure Reviewed by: Serapheim Dimitropoulos <serapheim@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> Authored by: Prakash Surya <prakash.surya@delphix.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Chris Dunlop <chris@onthe.net.au> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/8602 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/2bcb545 Closes #6779
2017-10-26 22:57:53 +03:00
.sp
Default value: \fB1048576\fR.
.RE
.sp
.ne 2
.na
\fBzfs_zil_clean_taskq_minalloc\fR (int)
.ad
.RS 12n
The number of taskq entries that are pre-populated when the taskq is first
created and are immediately available for use.
.sp
Default value: \fB1024\fR.
.RE
.sp
.ne 2
.na
\fBzfs_zil_clean_taskq_nthr_pct\fR (int)
.ad
.RS 12n
This controls the number of threads used by the dp_zil_clean_taskq. The default
value of 100% will create a maximum of one thread per cpu.
.sp
Fix percentage styling in zfs-module-parameters.5 Replace "percent" with "%", add bold to default values. Reviewed-by: bunder2015 <omfgbunder@gmail.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Amanakis <gamanakis@gmail.com> Closes #7018
2018-01-09 22:51:11 +03:00
Default value: \fB100\fR%.
OpenZFS 8558, 8602 - lwp_create() returns EAGAIN 8558 lwp_create() returns EAGAIN on system with more than 80K ZFS filesystems On a system with more than 80K ZFS filesystems, we've seen cases where lwp_create() will start to fail by returning EAGAIN. The problem being, for each of those 80K ZFS filesystems, a taskq will be created for each dataset as part of the ZIL for each dataset. Porting Notes: - The new nomem taskq kstat was dropped. - Added module options and documentation for new tunings zfs_zil_clean_taskq_nthr_pct, zfs_zil_clean_taskq_minalloc, zfs_zil_clean_taskq_maxalloc, and zfs_sync_taskq_batch_pct. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Sebastien Roy <sebastien.roy@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> Authored by: Prakash Surya <prakash.surya@delphix.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Chris Dunlop <chris@onthe.net.au> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/8558 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/216d772 8602 remove unused "dp_early_sync_tasks" field from "dsl_pool" structure Reviewed by: Serapheim Dimitropoulos <serapheim@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Approved by: Robert Mustacchi <rm@joyent.com> Authored by: Prakash Surya <prakash.surya@delphix.com> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Chris Dunlop <chris@onthe.net.au> Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/8602 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/2bcb545 Closes #6779
2017-10-26 22:57:53 +03:00
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
.ne 2
.na
\fBzil_replay_disable\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Disable intent logging replay. Can be disabled for recovery from corrupted
ZIL
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
.sp
.ne 2
.na
OpenZFS 7578 - Fix/improve some aspects of ZIL writing - After some ZIL changes 6 years ago zil_slog_limit got partially broken due to zl_itx_list_sz not updated when async itx'es upgraded to sync. Actually because of other changes about that time zl_itx_list_sz is not really required to implement the functionality, so this patch removes some unneeded broken code and variables. - Original idea of zil_slog_limit was to reduce chance of SLOG abuse by single heavy logger, that increased latency for other (more latency critical) loggers, by pushing heavy log out into the main pool instead of SLOG. Beside huge latency increase for heavy writers, this implementation caused double write of all data, since the log records were explicitly prepared for SLOG. Since we now have I/O scheduler, I've found it can be much more efficient to reduce priority of heavy logger SLOG writes from ZIO_PRIORITY_SYNC_WRITE to ZIO_PRIORITY_ASYNC_WRITE, while still leave them on SLOG. - Existing ZIL implementation had problem with space efficiency when it has to write large chunks of data into log blocks of limited size. In some cases efficiency stopped to almost as low as 50%. In case of ZIL stored on spinning rust, that also reduced log write speed in half, since head had to uselessly fly over allocated but not written areas. This change improves the situation by offloading problematic operations from z*_log_write() to zil_lwb_commit(), which knows real situation of log blocks allocation and can split large requests into pieces much more efficiently. Also as side effect it removes one of two data copy operations done by ZIL code WR_COPIED case. - While there, untangle and unify code of z*_log_write() functions. Also zfs_log_write() alike to zvol_log_write() can now handle writes crossing block boundary, that may also improve efficiency if ZPL is made to do that. Sponsored by: iXsystems, Inc. Authored by: Alexander Motin <mav@FreeBSD.org> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Andriy Gapon <avg@FreeBSD.org> Reviewed by: Steven Hartland <steven.hartland@multiplay.co.uk> Reviewed by: Brad Lewis <brad.lewis@delphix.com> Reviewed by: Richard Elling <Richard.Elling@RichardElling.com> Approved by: Robert Mustacchi <rm@joyent.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Richard Yao <ryao@gentoo.org> Ported-by: Giuseppe Di Natale <dinatale2@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/7578 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/aeb13ac Closes #6191
2017-06-09 19:15:37 +03:00
\fBzil_slog_bulk\fR (ulong)
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.ad
.RS 12n
OpenZFS 7578 - Fix/improve some aspects of ZIL writing - After some ZIL changes 6 years ago zil_slog_limit got partially broken due to zl_itx_list_sz not updated when async itx'es upgraded to sync. Actually because of other changes about that time zl_itx_list_sz is not really required to implement the functionality, so this patch removes some unneeded broken code and variables. - Original idea of zil_slog_limit was to reduce chance of SLOG abuse by single heavy logger, that increased latency for other (more latency critical) loggers, by pushing heavy log out into the main pool instead of SLOG. Beside huge latency increase for heavy writers, this implementation caused double write of all data, since the log records were explicitly prepared for SLOG. Since we now have I/O scheduler, I've found it can be much more efficient to reduce priority of heavy logger SLOG writes from ZIO_PRIORITY_SYNC_WRITE to ZIO_PRIORITY_ASYNC_WRITE, while still leave them on SLOG. - Existing ZIL implementation had problem with space efficiency when it has to write large chunks of data into log blocks of limited size. In some cases efficiency stopped to almost as low as 50%. In case of ZIL stored on spinning rust, that also reduced log write speed in half, since head had to uselessly fly over allocated but not written areas. This change improves the situation by offloading problematic operations from z*_log_write() to zil_lwb_commit(), which knows real situation of log blocks allocation and can split large requests into pieces much more efficiently. Also as side effect it removes one of two data copy operations done by ZIL code WR_COPIED case. - While there, untangle and unify code of z*_log_write() functions. Also zfs_log_write() alike to zvol_log_write() can now handle writes crossing block boundary, that may also improve efficiency if ZPL is made to do that. Sponsored by: iXsystems, Inc. Authored by: Alexander Motin <mav@FreeBSD.org> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Andriy Gapon <avg@FreeBSD.org> Reviewed by: Steven Hartland <steven.hartland@multiplay.co.uk> Reviewed by: Brad Lewis <brad.lewis@delphix.com> Reviewed by: Richard Elling <Richard.Elling@RichardElling.com> Approved by: Robert Mustacchi <rm@joyent.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Richard Yao <ryao@gentoo.org> Ported-by: Giuseppe Di Natale <dinatale2@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/7578 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/aeb13ac Closes #6191
2017-06-09 19:15:37 +03:00
Limit SLOG write size per commit executed with synchronous priority.
Any writes above that will be executed with lower (asynchronous) priority
to limit potential SLOG device abuse by single active ZIL writer.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
OpenZFS 7578 - Fix/improve some aspects of ZIL writing - After some ZIL changes 6 years ago zil_slog_limit got partially broken due to zl_itx_list_sz not updated when async itx'es upgraded to sync. Actually because of other changes about that time zl_itx_list_sz is not really required to implement the functionality, so this patch removes some unneeded broken code and variables. - Original idea of zil_slog_limit was to reduce chance of SLOG abuse by single heavy logger, that increased latency for other (more latency critical) loggers, by pushing heavy log out into the main pool instead of SLOG. Beside huge latency increase for heavy writers, this implementation caused double write of all data, since the log records were explicitly prepared for SLOG. Since we now have I/O scheduler, I've found it can be much more efficient to reduce priority of heavy logger SLOG writes from ZIO_PRIORITY_SYNC_WRITE to ZIO_PRIORITY_ASYNC_WRITE, while still leave them on SLOG. - Existing ZIL implementation had problem with space efficiency when it has to write large chunks of data into log blocks of limited size. In some cases efficiency stopped to almost as low as 50%. In case of ZIL stored on spinning rust, that also reduced log write speed in half, since head had to uselessly fly over allocated but not written areas. This change improves the situation by offloading problematic operations from z*_log_write() to zil_lwb_commit(), which knows real situation of log blocks allocation and can split large requests into pieces much more efficiently. Also as side effect it removes one of two data copy operations done by ZIL code WR_COPIED case. - While there, untangle and unify code of z*_log_write() functions. Also zfs_log_write() alike to zvol_log_write() can now handle writes crossing block boundary, that may also improve efficiency if ZPL is made to do that. Sponsored by: iXsystems, Inc. Authored by: Alexander Motin <mav@FreeBSD.org> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Andriy Gapon <avg@FreeBSD.org> Reviewed by: Steven Hartland <steven.hartland@multiplay.co.uk> Reviewed by: Brad Lewis <brad.lewis@delphix.com> Reviewed by: Richard Elling <Richard.Elling@RichardElling.com> Approved by: Robert Mustacchi <rm@joyent.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Richard Yao <ryao@gentoo.org> Ported-by: Giuseppe Di Natale <dinatale2@llnl.gov> OpenZFS-issue: https://www.illumos.org/issues/7578 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/aeb13ac Closes #6191
2017-06-09 19:15:37 +03:00
Default value: \fB786,432\fR.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.RE
OpenZFS 9403 - assertion failed in arc_buf_destroy() Assertion failed in arc_buf_destroy() when concurrently reading block with checksum error. Porting notes: * The ability to zinject decompression errors has been added, but this only works at the zio_decompress() level, where we have all of the info we need to match against the user's zinject options. * The decompress_fault test has been added to test the new zinject functionality * We attempted to set zio_decompress_fail_fraction to (1 << 18) in ztest for further test coverage. Although this did uncover a few low priority issues, this unfortuantely also causes ztest to ASSERT in many locations where the code is working correctly since it is designed to fail on IO errors. Developers can manually set this variable with the '-o' option to find and debug issues. Authored by: Matt Ahrens <mahrens@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Paul Dagnelie <pcd@delphix.com> Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Matt Ahrens <mahrens@delphix.com> Ported-by: Tom Caputi <tcaputi@datto.com> OpenZFS-issue: https://illumos.org/issues/9403 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/fa98e487a9 Closes #7822
2018-08-29 21:33:33 +03:00
.sp
.ne 2
.na
\fBzio_decompress_fail_fraction\fR (int)
.ad
.RS 12n
If non-zero, this value represents the denominator of the probability that zfs
should induce a decompression failure. For instance, for a 5% decompression
failure rate, this value should be set to 20.
.sp
Default value: \fB0\fR.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
.ne 2
.na
\fBzio_delay_max\fR (int)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
A zevent will be logged if a ZIO operation takes more than N milliseconds to
SIMD implementation of vdev_raidz generate and reconstruct routines This is a new implementation of RAIDZ1/2/3 routines using x86_64 scalar, SSE, and AVX2 instruction sets. Included are 3 parity generation routines (P, PQ, and PQR) and 7 reconstruction routines, for all RAIDZ level. On module load, a quick benchmark of supported routines will select the fastest for each operation and they will be used at runtime. Original implementation is still present and can be selected via module parameter. Patch contains: - specialized gen/rec routines for all RAIDZ levels, - new scalar raidz implementation (unrolled), - two x86_64 SIMD implementations (SSE and AVX2 instructions sets), - fastest routines selected on module load (benchmark). - cmd/raidz_test - verify and benchmark all implementations - added raidz_test to the ZFS Test Suite New zfs module parameters: - zfs_vdev_raidz_impl (str): selects the implementation to use. On module load, the parameter will only accept first 3 options, and the other implementations can be set once module is finished loading. Possible values for this option are: "fastest" - use the fastest math available "original" - use the original raidz code "scalar" - new scalar impl "sse" - new SSE impl if available "avx2" - new AVX2 impl if available See contents of `/sys/module/zfs/parameters/zfs_vdev_raidz_impl` to get the list of supported values. If an implementation is not supported on the system, it will not be shown. Currently selected option is enclosed in `[]`. Signed-off-by: Gvozden Neskovic <neskovic@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4328
2016-04-25 11:04:31 +03:00
complete. Note that this is only a logging facility, not a timeout on
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
operations.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Default value: \fB30,000\fR.
.RE
OpenZFS 7090 - zfs should throttle allocations OpenZFS 7090 - zfs should throttle allocations Authored by: George Wilson <george.wilson@delphix.com> Reviewed by: Alex Reece <alex@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Paul Dagnelie <paul.dagnelie@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Sebastien Roy <sebastien.roy@delphix.com> Approved by: Matthew Ahrens <mahrens@delphix.com> Ported-by: Don Brady <don.brady@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> When write I/Os are issued, they are issued in block order but the ZIO pipeline will drive them asynchronously through the allocation stage which can result in blocks being allocated out-of-order. It would be nice to preserve as much of the logical order as possible. In addition, the allocations are equally scattered across all top-level VDEVs but not all top-level VDEVs are created equally. The pipeline should be able to detect devices that are more capable of handling allocations and should allocate more blocks to those devices. This allows for dynamic allocation distribution when devices are imbalanced as fuller devices will tend to be slower than empty devices. The change includes a new pool-wide allocation queue which would throttle and order allocations in the ZIO pipeline. The queue would be ordered by issued time and offset and would provide an initial amount of allocation of work to each top-level vdev. The allocation logic utilizes a reservation system to reserve allocations that will be performed by the allocator. Once an allocation is successfully completed it's scheduled on a given top-level vdev. Each top-level vdev maintains a maximum number of allocations that it can handle (mg_alloc_queue_depth). The pool-wide reserved allocations (top-levels * mg_alloc_queue_depth) are distributed across the top-level vdevs metaslab groups and round robin across all eligible metaslab groups to distribute the work. As top-levels complete their work, they receive additional work from the pool-wide allocation queue until the allocation queue is emptied. OpenZFS-issue: https://www.illumos.org/issues/7090 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/4756c3d7 Closes #5258 Porting Notes: - Maintained minimal stack in zio_done - Preserve linux-specific io sizes in zio_write_compress - Added module params and documentation - Updated to use optimize AVL cmp macros
2016-10-14 03:59:18 +03:00
.sp
.ne 2
.na
\fBzio_dva_throttle_enabled\fR (int)
.ad
.RS 12n
Throttle block allocations in the ZIO pipeline. This allows for
dynamic allocation distribution when devices are imbalanced.
Update documentation for zfs_vdev_queue_depth_pct It was documented as being related to zfs_vdev_async_max_active when it is actually related to zfs_vdev_async_write_max_active. Also, expand the documentation to describe the allocation throttle which was introduced as part of OpenZFS 7090 in 3dfb57a. Reviewed-by: Richard Yao <ryao@gentoo.org> Reviewed-by: Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Tim Chase <tim@chase2k.com> Closes #6064
2017-04-25 07:01:04 +03:00
When enabled, the maximum number of pending allocations per top-level vdev
is limited by \fBzfs_vdev_queue_depth_pct\fR.
OpenZFS 7090 - zfs should throttle allocations OpenZFS 7090 - zfs should throttle allocations Authored by: George Wilson <george.wilson@delphix.com> Reviewed by: Alex Reece <alex@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Paul Dagnelie <paul.dagnelie@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Sebastien Roy <sebastien.roy@delphix.com> Approved by: Matthew Ahrens <mahrens@delphix.com> Ported-by: Don Brady <don.brady@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> When write I/Os are issued, they are issued in block order but the ZIO pipeline will drive them asynchronously through the allocation stage which can result in blocks being allocated out-of-order. It would be nice to preserve as much of the logical order as possible. In addition, the allocations are equally scattered across all top-level VDEVs but not all top-level VDEVs are created equally. The pipeline should be able to detect devices that are more capable of handling allocations and should allocate more blocks to those devices. This allows for dynamic allocation distribution when devices are imbalanced as fuller devices will tend to be slower than empty devices. The change includes a new pool-wide allocation queue which would throttle and order allocations in the ZIO pipeline. The queue would be ordered by issued time and offset and would provide an initial amount of allocation of work to each top-level vdev. The allocation logic utilizes a reservation system to reserve allocations that will be performed by the allocator. Once an allocation is successfully completed it's scheduled on a given top-level vdev. Each top-level vdev maintains a maximum number of allocations that it can handle (mg_alloc_queue_depth). The pool-wide reserved allocations (top-levels * mg_alloc_queue_depth) are distributed across the top-level vdevs metaslab groups and round robin across all eligible metaslab groups to distribute the work. As top-levels complete their work, they receive additional work from the pool-wide allocation queue until the allocation queue is emptied. OpenZFS-issue: https://www.illumos.org/issues/7090 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/4756c3d7 Closes #5258 Porting Notes: - Maintained minimal stack in zio_done - Preserve linux-specific io sizes in zio_write_compress - Added module params and documentation - Updated to use optimize AVL cmp macros
2016-10-14 03:59:18 +03:00
.sp
Revert "Disable zio_dva_throttle_enabled by default" Enable zio_dva_throttle_enabled=1 by default. Subsequent testing has been unable to reproduce the suspected regression. Tested-by: kernelOfTruth kerneloftruth@gmail.com Reviewed-by: Olaf Faaland <faaland1@llnl.gov> Signed-off-by: Brian Behlendorf behlendorf1@llnl.gov Reverts #5335 Closes #5289 Closes #5457
2016-12-08 23:57:42 +03:00
Default value: \fB1\fR.
OpenZFS 7090 - zfs should throttle allocations OpenZFS 7090 - zfs should throttle allocations Authored by: George Wilson <george.wilson@delphix.com> Reviewed by: Alex Reece <alex@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Paul Dagnelie <paul.dagnelie@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Sebastien Roy <sebastien.roy@delphix.com> Approved by: Matthew Ahrens <mahrens@delphix.com> Ported-by: Don Brady <don.brady@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> When write I/Os are issued, they are issued in block order but the ZIO pipeline will drive them asynchronously through the allocation stage which can result in blocks being allocated out-of-order. It would be nice to preserve as much of the logical order as possible. In addition, the allocations are equally scattered across all top-level VDEVs but not all top-level VDEVs are created equally. The pipeline should be able to detect devices that are more capable of handling allocations and should allocate more blocks to those devices. This allows for dynamic allocation distribution when devices are imbalanced as fuller devices will tend to be slower than empty devices. The change includes a new pool-wide allocation queue which would throttle and order allocations in the ZIO pipeline. The queue would be ordered by issued time and offset and would provide an initial amount of allocation of work to each top-level vdev. The allocation logic utilizes a reservation system to reserve allocations that will be performed by the allocator. Once an allocation is successfully completed it's scheduled on a given top-level vdev. Each top-level vdev maintains a maximum number of allocations that it can handle (mg_alloc_queue_depth). The pool-wide reserved allocations (top-levels * mg_alloc_queue_depth) are distributed across the top-level vdevs metaslab groups and round robin across all eligible metaslab groups to distribute the work. As top-levels complete their work, they receive additional work from the pool-wide allocation queue until the allocation queue is emptied. OpenZFS-issue: https://www.illumos.org/issues/7090 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/4756c3d7 Closes #5258 Porting Notes: - Maintained minimal stack in zio_done - Preserve linux-specific io sizes in zio_write_compress - Added module params and documentation - Updated to use optimize AVL cmp macros
2016-10-14 03:59:18 +03:00
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
.ne 2
.na
\fBzio_requeue_io_start_cut_in_line\fR (int)
.ad
.RS 12n
Prioritize requeued I/O
.sp
Default value: \fB0\fR.
.RE
Make zio_taskq_batch_pct user configurable Adds zio_taskq_batch_pct as an exported module parameter, allowing users to modify it at module load time. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4110
2015-12-16 22:22:32 +03:00
.sp
.ne 2
.na
\fBzio_taskq_batch_pct\fR (uint)
.ad
.RS 12n
Percentage of online CPUs (or CPU cores, etc) which will run a worker thread
for IO. These workers are responsible for IO work such as compression and
checksum calculations. Fractional number of CPUs will be rounded down.
.sp
The default value of 75 was chosen to avoid using all CPUs which can result in
latency issues and inconsistent application performance, especially when high
compression is enabled.
.sp
Default value: \fB75\fR.
.RE
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
.ne 2
.na
\fBzvol_inhibit_dev\fR (uint)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Do not create zvol device nodes. This may slightly improve startup time on
systems with a very large number of zvols.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
.sp
.ne 2
.na
\fBzvol_major\fR (uint)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Major number for zvol block devices
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Default value: \fB230\fR.
.RE
.sp
.ne 2
.na
\fBzvol_max_discard_blocks\fR (ulong)
.ad
.RS 12n
Improve zfs-module-parameters(5) Various rewrites to the descriptions of module parameters. Corrects spelling mistakes, makes descriptions them more user-friendly and describes some ZFS quirks which should be understood before changing parameter values. Signed-off-by: DHE <git@dehacked.net> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #4671
2015-12-30 20:44:46 +03:00
Discard (aka TRIM) operations done on zvols will be done in batches of this
many blocks, where block size is determined by the \fBvolblocksize\fR property
of a zvol.
Document ZFS module parameters. This is a first draft of a zfs-module-parameters(5) man page. I have just extracted the parameter name and its description with modinfo, then checked the source what type it is and its default value. This will need more work, preferably someone that actually know these values and what to use them for. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1856
2013-11-16 10:52:54 +04:00
.sp
Default value: \fB16,384\fR.
.RE
Prefetch start and end of volumes When adding a zvol to the system prefetch zvol_prefetch_bytes from the start and end of the volume. Prefetching these regions of the volume is desirable because they are likely to be accessed immediately by blkid(8), the kernel scanning for a partition table, or another task which probes the devices. Signed-off-by: Richard Yao <ryao@gentoo.org> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #3659
2015-08-18 23:51:20 +03:00
.sp
.ne 2
.na
\fBzvol_prefetch_bytes\fR (uint)
.ad
.RS 12n
When adding a zvol to the system prefetch \fBzvol_prefetch_bytes\fR
from the start and end of the volume. Prefetching these regions
of the volume is desirable because they are likely to be accessed
immediately by \fBblkid(8)\fR or by the kernel scanning for a partition
table.
.sp
Default value: \fB131,072\fR.
.RE
Reinstate zvol_taskq to fix aio on zvol Commit 37f9dac removed the zvol_taskq for processing zvol requests. This was removed as part of switching to make_request_fn and was motivated by a concern at the time over dispatch latency. However, this also made all bio request synchronous, and caused serious performance issues as the bio submitter would wait for every bio it submitted, effectively making the IO depth 1. This patch reinstate zvol_taskq, and to make sure overlapped I/Os are ordered properly, we take range lock in zvol_request, and pass it along with bio to the I/O functions zvol_{write,discard,read}. In order to facilitate benchmarks a zvol_request_sync module option was added to switch between sync and async request handling. For the moment, the default behavior is synchronous but this is likely to change pending additional testing. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Chunwei Chen <david.chen@osnexus.com> Closes #5824
2017-02-23 03:08:04 +03:00
.sp
.ne 2
.na
\fBzvol_request_sync\fR (uint)
.ad
.RS 12n
When processing I/O requests for a zvol submit them synchronously. This
effectively limits the queue depth to 1 for each I/O submitter. When set
to 0 requests are handled asynchronously by a thread pool. The number of
requests which can be handled concurrently is controller by \fBzvol_threads\fR.
.sp
Default to zvol_request_async=0 Change the default ZVOL behavior so requests are handled asynchronously. This behavior is functionally the same as in the zfs-0.6.4 release. Reviewed-by: Chunwei Chen <david.chen@osnexus.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #5902
2017-05-03 03:37:14 +03:00
Default value: \fB0\fR.
Reinstate zvol_taskq to fix aio on zvol Commit 37f9dac removed the zvol_taskq for processing zvol requests. This was removed as part of switching to make_request_fn and was motivated by a concern at the time over dispatch latency. However, this also made all bio request synchronous, and caused serious performance issues as the bio submitter would wait for every bio it submitted, effectively making the IO depth 1. This patch reinstate zvol_taskq, and to make sure overlapped I/Os are ordered properly, we take range lock in zvol_request, and pass it along with bio to the I/O functions zvol_{write,discard,read}. In order to facilitate benchmarks a zvol_request_sync module option was added to switch between sync and async request handling. For the moment, the default behavior is synchronous but this is likely to change pending additional testing. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Chunwei Chen <david.chen@osnexus.com> Closes #5824
2017-02-23 03:08:04 +03:00
.RE
.sp
.ne 2
.na
\fBzvol_threads\fR (uint)
.ad
.RS 12n
Max number of threads which can handle zvol I/O requests concurrently.
.sp
Default value: \fB32\fR.
.RE
Add port of FreeBSD 'volmode' property The volmode property may be set to control the visibility of ZVOL block devices. This allow switching ZVOL between three modes: full - existing fully functional behaviour (default) dev - hide partitions on ZVOL block devices none - not exposing volumes outside ZFS Additionally the new zvol_volmode module parameter can be used to control the default behaviour. This functionality can be used, for instance, on "backup" pools to avoid cluttering /dev with unneeded zd* devices. Original-patch-by: mav <mav@FreeBSD.org> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Ported-by: loli10K <ezomori.nozomu@gmail.com> Signed-off-by: loli10K <ezomori.nozomu@gmail.com> FreeBSD-commit: https://github.com/freebsd/freebsd/commit/dd28e6bb Closes #1796 Closes #3438 Closes #6233
2017-07-12 23:05:37 +03:00
.sp
.ne 2
.na
\fBzvol_volmode\fR (uint)
.ad
.RS 12n
Defines zvol block devices behaviour when \fBvolmode\fR is set to \fBdefault\fR.
Valid values are \fB1\fR (full), \fB2\fR (dev) and \fB3\fR (none).
.sp
Default value: \fB1\fR.
.RE
Update documentation for new parameter "zfs_qat_disable" Update documentation in zfs-module-parameters.5 for new parameter "zfs_qat_disable" which was introduced by #5846. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Weigang Li <weigang.li@intel.com> Closes #5914
2017-03-27 22:33:57 +03:00
.sp
.ne 2
.na
\fBzfs_qat_disable\fR (int)
.ad
.RS 12n
QAT support for AES-GCM This patch adds support for acceleration of AES-GCM encryption with Intel Quick Assist Technology. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Chengfeix Zhu <chengfeix.zhu@intel.com> Signed-off-by: Weigang Li <weigang.li@intel.com> Signed-off-by: Tom Caputi <tcaputi@datto.com> Closes #7282
2018-03-10 00:37:15 +03:00
This tunable disables qat hardware acceleration for gzip compression and.
AES-GCM encryption. It is available only if qat acceleration is compiled in
and the qat driver is present.
Update documentation for new parameter "zfs_qat_disable" Update documentation in zfs-module-parameters.5 for new parameter "zfs_qat_disable" which was introduced by #5846. Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Weigang Li <weigang.li@intel.com> Closes #5914
2017-03-27 22:33:57 +03:00
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
Illumos #4045 write throttle & i/o scheduler performance work 4045 zfs write throttle & i/o scheduler performance work 1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync read, sync write, async read, async write, and scrub/resilver. The scheduler issues a number of concurrent i/os from each class to the device. Once a class has been selected, an i/o is selected from this class using either an elevator algorithem (async, scrub classes) or FIFO (sync classes). The number of concurrent async write i/os is tuned dynamically based on i/o load, to achieve good sync i/o latency when there is not a high load of writes, and good write throughput when there is. See the block comment in vdev_queue.c (reproduced below) for more details. 2. The write throttle (dsl_pool_tempreserve_space() and txg_constrain_throughput()) is rewritten to produce much more consistent delays when under constant load. The new write throttle is based on the amount of dirty data, rather than guesses about future performance of the system. When there is a lot of dirty data, each transaction (e.g. write() syscall) will be delayed by the same small amount. This eliminates the "brick wall of wait" that the old write throttle could hit, causing all transactions to wait several seconds until the next txg opens. One of the keys to the new write throttle is decrementing the amount of dirty data as i/o completes, rather than at the end of spa_sync(). Note that the write throttle is only applied once the i/o scheduler is issuing the maximum number of outstanding async writes. See the block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for more details. This diff has several other effects, including: * the commonly-tuned global variable zfs_vdev_max_pending has been removed; use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead. * the size of each txg (meaning the amount of dirty data written, and thus the time it takes to write out) is now controlled differently. There is no longer an explicit time goal; the primary determinant is amount of dirty data. Systems that are under light or medium load will now often see that a txg is always syncing, but the impact to performance (e.g. read latency) is minimal. Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this. * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression, checksum, etc. This improves latency by not allowing these CPU-intensive tasks to consume all CPU (on machines with at least 4 CPU's; the percentage is rounded up). --matt APPENDIX: problems with the current i/o scheduler The current ZFS i/o scheduler (vdev_queue.c) is deadline based. The problem with this is that if there are always i/os pending, then certain classes of i/os can see very long delays. For example, if there are always synchronous reads outstanding, then no async writes will be serviced until they become "past due". One symptom of this situation is that each pass of the txg sync takes at least several seconds (typically 3 seconds). If many i/os become "past due" (their deadline is in the past), then we must service all of these overdue i/os before any new i/os. This happens when we enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in the future. If we can't complete all the i/os in 2.5 seconds (e.g. because there were always reads pending), then these i/os will become past due. Now we must service all the "async" writes (which could be hundreds of megabytes) before we service any reads, introducing considerable latency to synchronous i/os (reads or ZIL writes). Notes on porting to ZFS on Linux: - zio_t gained new members io_physdone and io_phys_children. Because object caches in the Linux port call the constructor only once at allocation time, objects may contain residual data when retrieved from the cache. Therefore zio_create() was updated to zero out the two new fields. - vdev_mirror_pending() relied on the depth of the per-vdev pending queue (vq->vq_pending_tree) to select the least-busy leaf vdev to read from. This tree has been replaced by vq->vq_active_tree which is now used for the same purpose. - vdev_queue_init() used the value of zfs_vdev_max_pending to determine the number of vdev I/O buffers to pre-allocate. That global no longer exists, so we instead use the sum of the *_max_active values for each of the five I/O classes described above. - The Illumos implementation of dmu_tx_delay() delays a transaction by sleeping in condition variable embedded in the thread (curthread->t_delay_cv). We do not have an equivalent CV to use in Linux, so this change replaced the delay logic with a wrapper called zfs_sleep_until(). This wrapper could be adopted upstream and in other downstream ports to abstract away operating system-specific delay logic. - These tunables are added as module parameters, and descriptions added to the zfs-module-parameters.5 man page. spa_asize_inflation zfs_deadman_synctime_ms zfs_vdev_max_active zfs_vdev_async_write_active_min_dirty_percent zfs_vdev_async_write_active_max_dirty_percent zfs_vdev_async_read_max_active zfs_vdev_async_read_min_active zfs_vdev_async_write_max_active zfs_vdev_async_write_min_active zfs_vdev_scrub_max_active zfs_vdev_scrub_min_active zfs_vdev_sync_read_max_active zfs_vdev_sync_read_min_active zfs_vdev_sync_write_max_active zfs_vdev_sync_write_min_active zfs_dirty_data_max_percent zfs_delay_min_dirty_percent zfs_dirty_data_max_max_percent zfs_dirty_data_max zfs_dirty_data_max_max zfs_dirty_data_sync zfs_delay_scale The latter four have type unsigned long, whereas they are uint64_t in Illumos. This accommodates Linux's module_param() supported types, but means they may overflow on 32-bit architectures. The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most likely to overflow on 32-bit systems, since they express physical RAM sizes in bytes. In fact, Illumos initializes zfs_dirty_data_max_max to 2^32 which does overflow. To resolve that, this port instead initializes it in arc_init() to 25% of physical RAM, and adds the tunable zfs_dirty_data_max_max_percent to override that percentage. While this solution doesn't completely avoid the overflow issue, it should be a reasonable default for most systems, and the minority of affected systems can work around the issue by overriding the defaults. - Fixed reversed logic in comment above zfs_delay_scale declaration. - Clarified comments in vdev_queue.c regarding when per-queue minimums take effect. - Replaced dmu_tx_write_limit in the dmu_tx kstat file with dmu_tx_dirty_delay and dmu_tx_dirty_over_max. The first counts how many times a transaction has been delayed because the pool dirty data has exceeded zfs_delay_min_dirty_percent. The latter counts how many times the pool dirty data has exceeded zfs_dirty_data_max (which we expect to never happen). - The original patch would have regressed the bug fixed in zfsonlinux/zfs@c418410, which prevented users from setting the zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE. A similar fix is added to vdev_queue_aggregate(). - In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the heap instead of the stack. In Linux we can't afford such large structures on the stack. Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Ned Bass <bass6@llnl.gov> Reviewed by: Brendan Gregg <brendan.gregg@joyent.com> Approved by: Robert Mustacchi <rm@joyent.com> References: http://www.illumos.org/issues/4045 illumos/illumos-gate@69962b5647e4a8b9b14998733b765925381b727e Ported-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1913
2013-08-29 07:01:20 +04:00
.SH ZFS I/O SCHEDULER
ZFS issues I/O operations to leaf vdevs to satisfy and complete I/Os.
The I/O scheduler determines when and in what order those operations are
issued. The I/O scheduler divides operations into five I/O classes
prioritized in the following order: sync read, sync write, async read,
async write, and scrub/resilver. Each queue defines the minimum and
maximum number of concurrent operations that may be issued to the
device. In addition, the device has an aggregate maximum,
\fBzfs_vdev_max_active\fR. Note that the sum of the per-queue minimums
must not exceed the aggregate maximum. If the sum of the per-queue
maximums exceeds the aggregate maximum, then the number of active I/Os
may reach \fBzfs_vdev_max_active\fR, in which case no further I/Os will
be issued regardless of whether all per-queue minimums have been met.
.sp
For many physical devices, throughput increases with the number of
concurrent operations, but latency typically suffers. Further, physical
devices typically have a limit at which more concurrent operations have no
effect on throughput or can actually cause it to decrease.
.sp
The scheduler selects the next operation to issue by first looking for an
I/O class whose minimum has not been satisfied. Once all are satisfied and
the aggregate maximum has not been hit, the scheduler looks for classes
whose maximum has not been satisfied. Iteration through the I/O classes is
done in the order specified above. No further operations are issued if the
aggregate maximum number of concurrent operations has been hit or if there
are no operations queued for an I/O class that has not hit its maximum.
Every time an I/O is queued or an operation completes, the I/O scheduler
looks for new operations to issue.
.sp
In general, smaller max_active's will lead to lower latency of synchronous
operations. Larger max_active's may lead to higher overall throughput,
depending on underlying storage.
.sp
The ratio of the queues' max_actives determines the balance of performance
between reads, writes, and scrubs. E.g., increasing
\fBzfs_vdev_scrub_max_active\fR will cause the scrub or resilver to complete
more quickly, but reads and writes to have higher latency and lower throughput.
.sp
All I/O classes have a fixed maximum number of outstanding operations
except for the async write class. Asynchronous writes represent the data
that is committed to stable storage during the syncing stage for
transaction groups. Transaction groups enter the syncing state
periodically so the number of queued async writes will quickly burst up
and then bleed down to zero. Rather than servicing them as quickly as
possible, the I/O scheduler changes the maximum number of active async
write I/Os according to the amount of dirty data in the pool. Since
both throughput and latency typically increase with the number of
concurrent operations issued to physical devices, reducing the
burstiness in the number of concurrent operations also stabilizes the
response time of operations from other -- and in particular synchronous
-- queues. In broad strokes, the I/O scheduler will issue more
concurrent operations from the async write queue as there's more dirty
data in the pool.
.sp
Async Writes
.sp
The number of concurrent operations issued for the async write I/O class
follows a piece-wise linear function defined by a few adjustable points.
.nf
| o---------| <-- zfs_vdev_async_write_max_active
^ | /^ |
| | / | |
active | / | |
I/O | / | |
count | / | |
| / | |
|-------o | | <-- zfs_vdev_async_write_min_active
0|_______^______|_________|
0% | | 100% of zfs_dirty_data_max
| |
| `-- zfs_vdev_async_write_active_max_dirty_percent
`--------- zfs_vdev_async_write_active_min_dirty_percent
.fi
Until the amount of dirty data exceeds a minimum percentage of the dirty
data allowed in the pool, the I/O scheduler will limit the number of
concurrent operations to the minimum. As that threshold is crossed, the
number of concurrent operations issued increases linearly to the maximum at
the specified maximum percentage of the dirty data allowed in the pool.
.sp
Ideally, the amount of dirty data on a busy pool will stay in the sloped
part of the function between \fBzfs_vdev_async_write_active_min_dirty_percent\fR
and \fBzfs_vdev_async_write_active_max_dirty_percent\fR. If it exceeds the
maximum percentage, this indicates that the rate of incoming data is
greater than the rate that the backend storage can handle. In this case, we
must further throttle incoming writes, as described in the next section.
.SH ZFS TRANSACTION DELAY
We delay transactions when we've determined that the backend storage
isn't able to accommodate the rate of incoming writes.
.sp
If there is already a transaction waiting, we delay relative to when
that transaction will finish waiting. This way the calculated delay time
is independent of the number of threads concurrently executing
transactions.
.sp
If we are the only waiter, wait relative to when the transaction
started, rather than the current time. This credits the transaction for
"time already served", e.g. reading indirect blocks.
.sp
The minimum time for a transaction to take is calculated as:
.nf
min_time = zfs_delay_scale * (dirty - min) / (max - dirty)
min_time is then capped at 100 milliseconds.
.fi
.sp
The delay has two degrees of freedom that can be adjusted via tunables. The
percentage of dirty data at which we start to delay is defined by
\fBzfs_delay_min_dirty_percent\fR. This should typically be at or above
\fBzfs_vdev_async_write_active_max_dirty_percent\fR so that we only start to
delay after writing at full speed has failed to keep up with the incoming write
rate. The scale of the curve is defined by \fBzfs_delay_scale\fR. Roughly speaking,
this variable determines the amount of delay at the midpoint of the curve.
.sp
.nf
delay
10ms +-------------------------------------------------------------*+
| *|
9ms + *+
| *|
8ms + *+
| * |
7ms + * +
| * |
6ms + * +
| * |
5ms + * +
| * |
4ms + * +
| * |
3ms + * +
| * |
2ms + (midpoint) * +
| | ** |
1ms + v *** +
| zfs_delay_scale ----------> ******** |
0 +-------------------------------------*********----------------+
0% <- zfs_dirty_data_max -> 100%
.fi
.sp
Note that since the delay is added to the outstanding time remaining on the
most recent transaction, the delay is effectively the inverse of IOPS.
Here the midpoint of 500us translates to 2000 IOPS. The shape of the curve
was chosen such that small changes in the amount of accumulated dirty data
in the first 3/4 of the curve yield relatively small differences in the
amount of delay.
.sp
The effects can be easier to understand when the amount of delay is
represented on a log scale:
.sp
.nf
delay
100ms +-------------------------------------------------------------++
+ +
| |
+ *+
10ms + *+
+ ** +
| (midpoint) ** |
+ | ** +
1ms + v **** +
+ zfs_delay_scale ----------> ***** +
| **** |
+ **** +
100us + ** +
+ * +
| * |
+ * +
10us + * +
+ +
| |
+ +
+--------------------------------------------------------------+
0% <- zfs_dirty_data_max -> 100%
.fi
.sp
Note here that only as the amount of dirty data approaches its limit does
the delay start to increase rapidly. The goal of a properly tuned system
should be to keep the amount of dirty data out of that range by first
ensuring that the appropriate limits are set for the I/O scheduler to reach
optimal throughput on the backend storage, and then by changing the value
of \fBzfs_delay_scale\fR to increase the steepness of the curve.
Reference in New Issue Copy Permalink