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Tony Nguyen 64b6c47d90 dbuf_hold_impl() cleanup to improve cached read performance 
Currently every dbuf_hold_impl() incurs kmem_alloc() and kmem_free()
which can be costly for cached read performance.

This change reverts the dbuf_hold_impl() fix stack commit, i.e.
fc5bb51f08 to eliminate the extra
kmem_alloc() and kmem_free() operations and improve cached read
performance. With the change, each dbuf_hold_impl() frame uses 40 bytes
more, total of 800 for 20 recursive levels. Linux kernel stack sizes are
8K and 16K for 32bit and 64bit, respectively, so stack overrun risk is
limited.

Sample stack output comparisons with 50 PB file and recordsize=512
Current code
 11)     2240      64   arc_alloc_buf+0x4a/0xd0 [zfs]
 12)     2176     264   dbuf_read_impl.constprop.16+0x2e3/0x7f0 [zfs]
 13)     1912     120   dbuf_read+0xe5/0x520 [zfs]
 14)     1792      56   dbuf_hold_impl_arg+0x572/0x630 [zfs]
 15)     1736      64   dbuf_hold_impl_arg+0x508/0x630 [zfs]
 16)     1672      64   dbuf_hold_impl_arg+0x508/0x630 [zfs]
 17)     1608      40   dbuf_hold_impl+0x23/0x40 [zfs]
 18)     1568      40   dbuf_hold_level+0x32/0x60 [zfs]
 19)     1528      16   dbuf_hold+0x16/0x20 [zfs]

dbuf_hold_impl() cleanup
 11)     2320      64   arc_alloc_buf+0x4a/0xd0 [zfs]
 12)     2256     264   dbuf_read_impl.constprop.17+0x2e3/0x7f0 [zfs]
 13)     1992     120   dbuf_read+0xe5/0x520 [zfs]
 14)     1872      96   dbuf_hold_impl+0x50f/0x5e0 [zfs]
 15)     1776     104   dbuf_hold_impl+0x4df/0x5e0 [zfs]
 16)     1672     104   dbuf_hold_impl+0x4df/0x5e0 [zfs]
 17)     1568      40   dbuf_hold_level+0x32/0x60 [zfs]
 18)     1528      16   dbuf_hold+0x16/0x20 [zfs]

Performance observations on 8K recordsize filesystem:
- 8/128/1024K at 1-128 sequential cached read, ~3% improvement

Testing done on Ubuntu 18.04 with 4.15 kernel, 8vCPUs and SSD storage on
VMware ESX.

Reviewed-by: Matt Ahrens <matt@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tony Nguyen <tony.nguyen@delphix.com>
Closes #9351
2019-10-03 15:33:38 -07:00
.github Fix typos 2019-09-02 18:17:39 -07:00
cmd OpenZFS restructuring - libzutil 2019-10-03 10:20:44 -07:00
config OpenZFS restructuring - libspl 2019-10-02 10:39:48 -07:00
contrib Fix for zfs-dracut regression 2019-10-01 12:54:27 -07:00
etc Workaround to avoid a race when /var/lib is a persistent dataset 2019-10-02 10:51:55 -07:00
include OpenZFS restructuring - libzfs 2019-10-03 10:33:16 -07:00
lib OpenZFS restructuring - libzfs 2019-10-03 10:33:16 -07:00
man Add warning for zfs_vdev_elevator option removal 2019-09-25 09:23:29 -07:00
module dbuf_hold_impl() cleanup to improve cached read performance 2019-10-03 15:33:38 -07:00
rpm Canonicalize Python shebangs 2019-09-12 13:32:32 -07:00
scripts kmodtool: depmod path 2019-09-11 11:14:50 -07:00
tests ZTS: Fix upgrade_readonly_pool 2019-10-03 09:39:13 -07:00
udev Restore :: in Makefile.am 2019-08-26 11:48:31 -07:00
.gitignore Perform KABI checks in parallel 2019-10-01 12:50:34 -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 OpenZFS restructuring - libspl 2019-10-02 10:39:48 -07:00
copy-builtin copy-builtin: SPL must be in Kbuild first (again) 2019-09-11 11:09:50 -07:00
COPYRIGHT OpenZFS restructuring - move platform specific sources 2019-09-06 11:26:26 -07:00
LICENSE Update build system and packaging 2018-05-29 16:00:33 -07:00
Makefile.am Perform KABI checks in parallel 2019-10-01 12:50:34 -07:00
META Tag 0.8.0 2019-05-21 11:11:41 -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.