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Matthew Ahrens 2bce8049c3 OpenZFS 7004 - dmu_tx_hold_zap() does dnode_hold() 7x on same object
Using a benchmark which has 32 threads creating 2 million files in the
same directory, on a machine with 16 CPU cores, I observed poor
performance. I noticed that dmu_tx_hold_zap() was using about 30% of
all CPU, and doing dnode_hold() 7 times on the same object (the ZAP
object that is being held).

dmu_tx_hold_zap() keeps a hold on the dnode_t the entire time it is
running, in dmu_tx_hold_t:txh_dnode, so it would be nice to use the
dnode_t that we already have in hand, rather than repeatedly calling
dnode_hold(). To do this, we need to pass the dnode_t down through
all the intermediate calls that dmu_tx_hold_zap() makes, making these
routines take the dnode_t* rather than an objset_t* and a uint64_t
object number. In particular, the following routines will need to have
analogous *_by_dnode() variants created:

dmu_buf_hold_noread()
dmu_buf_hold()
zap_lookup()
zap_lookup_norm()
zap_count_write()
zap_lockdir()
zap_count_write()

This can improve performance on the benchmark described above by 100%,
from 30,000 file creations per second to 60,000. (This improvement is on
top of that provided by working around the object allocation issue. Peak
performance of ~90,000 creations per second was observed with 8 CPUs;
adding CPUs past that decreased performance due to lock contention.) The
CPU used by dmu_tx_hold_zap() was reduced by 88%, from 340 CPU-seconds
to 40 CPU-seconds.

Sponsored by: Intel Corp.

Signed-off-by: Matthew Ahrens <mahrens@delphix.com>
Signed-off-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

OpenZFS-issue: https://www.illumos.org/issues/7004
OpenZFS-commit: https://github.com/openzfs/openzfs/pull/109
Closes #4641
Closes #4972
2016-08-19 12:48:03 -07:00
cmd zdb: fencepost error at zdb_cb.zcb_embedded_histogram[][] 2016-08-16 14:53:09 -07:00
config Add support for AVX-512 family of instruction sets 2016-08-16 14:10:33 -07:00
contrib Set proper dependency for string replacement targets 2016-08-02 10:28:29 -07:00
etc Set proper dependency for string replacement targets 2016-08-02 10:28:29 -07:00
include OpenZFS 7004 - dmu_tx_hold_zap() does dnode_hold() 7x on same object 2016-08-19 12:48:03 -07:00
lib Rework of fletcher_4 module 2016-08-16 14:11:55 -07:00
man Fletcher4 implementation using avx512f instruction set 2016-08-16 14:11:14 -07:00
module OpenZFS 7004 - dmu_tx_hold_zap() does dnode_hold() 7x on same object 2016-08-19 12:48:03 -07:00
rpm Add missing RPM BuildRequires 2016-05-23 10:33:42 -07:00
scripts zloop: print backtrace from core files 2016-07-25 11:47:21 -07:00
tests Update zfs_create_(009,010)_neg.ksh 2016-08-18 13:00:11 -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 OpenZFS 5997 - FRU field not set during pool creation and never updated 2016-08-12 13:06:48 -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 Add make lint target 2016-08-02 09:25:43 -07:00
META Tag zfs-0.6.5 2015-09-11 11:16:38 -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

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