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Matthew Ahrens cbb9154958 looping in metaslab_block_picker impacts performance on fragmented pools 
On fragmented pools with high-performance storage, the looping in
metaslab_block_picker() can become the performance-limiting bottleneck.
When looking for a larger block (e.g. a 128K block for the ZIL), we may
search through many free segments (up to hundreds of thousands) to find
one that is large enough to satisfy the allocation. This can take a long
time (up to dozens of ms), and is done while holding the ms_lock, which
other threads may spin waiting for.

When this performance problem is encountered, profiling will show
high CPU time in metaslab_block_picker, as well as in mutex_enter from
various callers.

The problem is very evident on a test system with a sync write workload
with 8K writes to a recordsize=8k filesystem, with 4TB of SSD storage,
84% full and 88% fragmented. It has also been observed on production
systems with 90TB of storage, 76% full and 87% fragmented.

The fix is to change metaslab_df_alloc() to search only up to 16MB from
the previous allocation (of this alignment). After that, we will pick a
segment that is of the exact size requested (or larger). This reduces
the number of iterations to a few hundred on fragmented pools (a ~100x
improvement).

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Paul Dagnelie <pcd@delphix.com>
Reviewed-by: Tony Nguyen <tony.nguyen@delphix.com>
Reviewed-by: George Wilson <george.wilson@delphix.com>
Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com>
Signed-off-by: Matthew Ahrens <mahrens@delphix.com>
External-issue: DLPX-62324
Closes #8877
2020-01-22 13:48:56 -08:00
.github Update CONTRIBUTING to point users to IRC as well as mailing list 2019-03-13 11:57:57 -07:00
cmd make zil max block size tunable 2020-01-22 13:48:56 -08:00
config Minor style cleanup 2019-09-25 11:27:49 -07:00
contrib Fix Plymouth passphrase prompt in initramfs script 2019-09-25 11:27:50 -07:00
etc New service that waits on zvol links to be created 2019-09-25 11:27:51 -07:00
include single-chunk scatter ABDs can be treated as linear 2020-01-22 13:48:56 -08:00
lib Always refuse receving non-resume stream when resume state exists 2019-09-25 11:27:51 -07:00
man looping in metaslab_block_picker impacts performance on fragmented pools 2020-01-22 13:48:56 -08:00
module looping in metaslab_block_picker impacts performance on fragmented pools 2020-01-22 13:48:56 -08:00
rpm BuildRequires libtirpc-devel needed for RHEL 8 2019-09-25 11:27:51 -07:00
scripts kmodtool: depmod path 2019-09-25 11:27:51 -07:00
tests Fix /etc/hostid on root pool deadlock 2019-09-25 11:27:51 -07:00
udev Add enclosure_symlinks option to vdev_id 2018-12-14 17:27:49 -08:00
.gitignore Linux 5.3 compat: Makefile subdir-m no longer supported 2019-09-25 11:27:50 -07:00
.gitmodules Add zimport.sh compatibility test script 2014-02-21 12:10:31 -08:00
.travis.yml Add .travis.yml 2017-11-13 09:18:18 -08:00
AUTHORS Update build system and packaging 2018-05-29 16:00:33 -07:00
autogen.sh Cause autogen.sh to fail if autoreconf fails 2018-07-06 09:27:37 -07:00
CODE_OF_CONDUCT.md Add CODE_OF_CONDUCT.md 2019-04-30 10:58:45 -07:00
configure.ac New service that waits on zvol links to be created 2019-09-25 11:27:51 -07:00
copy-builtin Allow copy-builtin to work with modified sources 2018-10-17 12:06:05 -07:00
COPYRIGHT Update build system and packaging 2018-05-29 16:00:33 -07:00
LICENSE Update build system and packaging 2018-05-29 16:00:33 -07:00
Makefile.am Fix out-of-tree build failures 2019-09-25 11:27:48 -07:00
META Tag zfs-0.8.2 2019-09-25 11:27:51 -07:00
NEWS Add NEWS file 2018-09-18 12:03:47 -07:00
NOTICE Update build system and packaging 2018-05-29 16:00:33 -07:00
README.md Explicitly state supported Linux versions 2018-05-30 20:11:19 -07:00
TEST Update build system and packaging 2018-05-29 16:00:33 -07:00
zfs.release.in Move zfs.release generation to configure step 2012-07-12 12:22:51 -07:00

README.md

img

ZFS on Linux is an advanced file system and volume manager which was originally developed for Solaris and is now maintained by the OpenZFS community.

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Official Resources

Installation

Full documentation for installing ZoL on your favorite Linux distribution can be found at our site.

Contribute & Develop

We have a separate document with contribution guidelines.

Release

ZFS on Linux is released under a CDDL license.
For more details see the NOTICE, LICENSE and COPYRIGHT files; UCRL-CODE-235197

Supported Kernels

  • The META file contains the officially recognized supported kernel versions.