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Stephen Blinick 8a2a9db8df OpenZFS 9076 - Adjust perf test concurrency settings
ZFS Performance test concurrency should be lowered for better latency

Work by Stephen Blinick.

Nightly performance runs typically consist of two levels of concurrency;
and both are fairly high.

Since the IO runs are to a ZFS filesystem, within a zpool, which is
based on some variable number of vdev's, the amount of IO driven to each
device is variable. Additionally, different device types (HDD vs SSD,
etc) can generally handle a different amount of concurrent IO before
saturating.

Nevertheless, in practice, it appears that most tests are well past the
concurrency saturation point and therefore both perform with the same
throughput, the maximum of the device. Because the queuedepth to the
device(s) is so high however, the latency is much higher than the best
possible at that throughput, and increases linearly with the increase in
concurrency.

This means that changes in code that impact latency during normal
operation (before saturation) may not be apparent when a large component
of the measured latency is from the IO sitting in a queue to be
serviced. Therefore, changing the concurrency settings is recommended

Authored by: Stephen Blinick <stephen.blinick@delphix.com>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed by: Dan Kimmel <dan.kimmel@delphix.com>
Reviewed by: John Wren Kennedy <jwk404@gmail.com>
Ported-by: John Wren Kennedy <jwk404@gmail.com>

OpenZFS-issue: https://www.illumos.org/issues/9076
OpenZFS-commit: https://github.com/openzfs/openzfs/pull/562
Upstream bug: DLPX-45477
Closes #7302
2018-03-15 10:51:00 -07:00
.github Reduce codecov PR comments 2018-01-09 11:15:55 -08:00
cmd Destroy makes full snap list before destroying 2018-03-12 15:24:08 -07:00
config Add kernel module auto-loading 2018-03-13 10:45:55 -07:00
contrib Fix some typos 2018-02-28 08:57:10 -08:00
etc Add kernel module auto-loading 2018-03-13 10:45:55 -07:00
include Fix race in trace point in zrl_add_impl 2018-03-12 11:27:02 -07:00
lib Add kernel module auto-loading 2018-03-13 10:45:55 -07:00
man OpenZFS 9188 - increase size of dbuf cache to reduce indirect block decompression 2018-03-13 10:52:48 -07:00
module receive_spill does not byte swap spill contents 2018-03-15 10:29:51 -07:00
rpm Add kernel module auto-loading 2018-03-13 10:45:55 -07:00
scripts Fix free memory calculation on v3.14+ 2018-02-23 08:50:06 -08:00
tests OpenZFS 9076 - Adjust perf test concurrency settings 2018-03-15 10:51:00 -07:00
udev Add kernel module auto-loading 2018-03-13 10:45:55 -07:00
.gitignore Add configure option to enable gcov analysis 2017-09-15 10:24:13 -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 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 Take user namespaces into account in policy checks 2018-03-07 15:40:42 -08:00
copy-builtin Fix copy-builtin to work with ASAN patch 2018-01-12 09:39:36 -08:00
COPYRIGHT Encryption patch follow-up 2017-10-11 16:54:48 -04:00
DISCLAIMER Fix minor typos and update marketing copy. 2013-03-21 12:51:06 -07:00
Makefile.am Allow make checkstyle and paxscript in build dir 2018-02-21 12:35:59 -08:00
META Tag zfs-0.7.0 2017-07-26 10:13:25 -07:00
OPENSOLARIS.LICENSE Add CDDL license file 2008-12-01 14:49:34 -08:00
README.markdown Add scan.coverity.com badge to README 2017-10-30 16:21:24 -07:00
TEST Refresh TEST file to include new variables 2017-11-08 11:09:30 -08:00
zfs.release.in Move zfs.release generation to configure step 2012-07-12 12:22:51 -07:00

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