mirror_zfs/module
Tony Nguyen 16f42e1b6d Use smaller default slack/delta value for schedule_hrtimeout_range()
For interrupt coalescing, cv_timedwait_hires() uses a 100us slack/delta
for calls to schedule_hrtimeout_range(). This 100us slack can be costly
for small writes.

This change improves small write performance by passing resolution `res`
parameter to schedule_hrtimeout_range() to be used as delta/slack. A new
tunable `spl_schedule_hrtimeout_slack_us` is added to preserve old
behavior when desired.

Performance observations on 8K recordsize filesystem:
- 8K random writes at 1-64 threads, up to 60% improvement for one thread
  and smaller gains as thread count increases. At >64 threads, 2-5%
  decrease in performance was observed.
- 8K sequential writes, similar 60% improvement for one thread and
  leveling out around 64 threads. At >64 threads, 5-10% decrease in
  performance was observed.
- 128K sequential write sees 1-5 for the 128K. No observed regression at
  high thread count.

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

Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Matt Ahrens <mahrens@delphix.com>
Signed-off-by: Tony Nguyen <tony.nguyen@delphix.com>
Closes #9217
2020-01-22 13:48:58 -08:00
..
avl Update build system and packaging 2018-05-29 16:00:33 -07:00
icp Minor style cleanup 2019-09-25 11:27:49 -07:00
lua Linux 5.3: Fix switch() fall though compiler errors 2019-09-25 11:27:50 -07:00
nvpair Use NV_ENCODE_NATIVE for nvlist encoding variable 2019-04-26 11:24:31 -07:00
spl Use smaller default slack/delta value for schedule_hrtimeout_range() 2020-01-22 13:48:58 -08:00
unicode Update build system and packaging 2018-05-29 16:00:33 -07:00
zcommon Minor style cleanup 2019-09-25 11:27:49 -07:00
zfs Use smaller default slack/delta value for schedule_hrtimeout_range() 2020-01-22 13:48:58 -08:00
.gitignore Prepare SPL repo to merge with ZFS repo 2018-05-29 14:51:39 -07:00
Makefile.in Linux 5.3 compat: Makefile subdir-m no longer supported 2019-09-25 11:27:50 -07:00