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Jinshan Xiong 9b7a83cbb6 OpenZFS 6988 spa_sync() spends half its time in dmu_objset_do_userquota_updates 
Using a benchmark which creates 2 million files in one TXG, I observe
that the thread running spa_sync() is on CPU almost the entire time we
are syncing, and therefore can be a performance bottleneck. About 50% of
the time in spa_sync() is in dmu_objset_do_userquota_updates().

The problem is that dmu_objset_do_userquota_updates() calls
zap_increment_int(DMU_USERUSED_OBJECT) once for every file that was
modified (or created). In this benchmark, all the files are owned by the
same user/group, so all 2 million calls to zap_increment_int() are
modifying the same entry in the zap. The same issue exists for the
DMU_GROUPUSED_OBJECT.

We should keep an in-memory map from user to space delta while we are
syncing, and when we finish, iterate over the in-memory map and modify
the ZAP once per entry. This reduces the number of calls to
zap_increment_int() from "number of objects modified" to "number of
owners/groups of modified files".

This reduced the time spent in spa_sync() in the file create benchmark
by ~33%, from 11 seconds to 7 seconds.

Upstream bugs: DLPX-44799
Ported by: Ned Bass <bass6@llnl.gov>

OpenZFS-issue: https://www.illumos.org/issues/6988
ZFSonLinux-issue: https://github.com/zfsonlinux/zfs/issues/4642
OpenZFS-commit: unmerged

Porting notes:
- Added curly braces around declaration of userquota_cache_t cache to
  quiet compiler warning;
- Handled the userobj accounting the same way it proposed in this path.

Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com>
2016-10-07 09:45:13 -07:00
cmd Add support for user/group dnode accounting & quota 2016-10-07 09:45:13 -07:00
config Explicit block device plugging when submitting multiple BIOs 2016-09-29 13:13:31 -07:00
contrib Use a different technique to detect whether to mount-zfs 2016-10-06 10:26:47 -07:00
etc Change /etc/mtab to /proc/self/mounts 2016-09-20 10:07:58 -07:00
include Add support for user/group dnode accounting & quota 2016-10-07 09:45:13 -07:00
lib Add support for user/group dnode accounting & quota 2016-10-07 09:45:13 -07:00
man Add support for user/group dnode accounting & quota 2016-10-07 09:45:13 -07:00
module OpenZFS 6988 spa_sync() spends half its time in dmu_objset_do_userquota_updates 2016-10-07 09:45:13 -07:00
rpm OpenZFS - Performance regression suite for zfstest 2016-09-08 16:18:28 -07:00
scripts Add icp kernel module to dkms build 2016-10-06 10:31:42 -07:00
tests Add support for user/group dnode accounting & quota 2016-10-07 09:45:13 -07:00
udev Set proper dependency for string replacement targets 2016-08-02 10:28:29 -07:00
.gitignore Illumos Crypto Port module added to enable native encryption in zfs 2016-07-20 10:43:30 -07:00
.gitmodules Add zimport.sh compatibility test script 2014-02-21 12:10:31 -08:00
AUTHORS Add a missing > to AUTHORS 2014-09-02 14:18:53 -07:00
autogen.sh build: do not call boilerplate ourself 2013-04-02 10:55:20 -07:00
configure.ac Add support for user/group dnode accounting & quota 2016-10-07 09:45:13 -07:00
copy-builtin Illumos Crypto Port module added to enable native encryption in zfs 2016-07-20 10:43:30 -07:00
COPYRIGHT Update ZED copyright boilerplate 2015-05-11 15:07:00 -07:00
DISCLAIMER Fix minor typos and update marketing copy. 2013-03-21 12:51:06 -07:00
Makefile.am OpenZFS 4185 - add new cryptographic checksums to ZFS: SHA-512, Skein, Edon-R 2016-10-03 14:51:15 -07:00
META Tag 0.7.0-rc1 2016-09-07 10:31:23 -07:00
OPENSOLARIS.LICENSE Add CDDL license file 2008-12-01 14:49:34 -08:00
README.markdown Fix minor typos and update marketing copy. 2013-03-21 12:51:06 -07:00
TEST Add the ZFS Test Suite 2016-03-16 13:46:16 -07:00
zfs-script-config.sh.in Illumos Crypto Port module added to enable native encryption in zfs 2016-07-20 10:43:30 -07:00
zfs.release.in Move zfs.release generation to configure step 2012-07-12 12:22:51 -07:00

README.markdown

Native ZFS for Linux!

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

ZFS on Linux, which is also known as ZoL, is currently feature complete. It includes fully functional and stable SPA, DMU, ZVOL, and ZPL layers.

Full documentation for installing ZoL on your favorite Linux distribution can be found at: http://zfsonlinux.org