Re: [PATCHv4 14/17] zsmalloc: make zspage lock preemptible

[Sergey Senozhatsky <senozhatsky@chromium.org>]

On (25/02/12 15:35), Yosry Ahmed wrote:
> > Difference at 95.0% confidence
> > 	-1.03219e+08 +/- 55308.7
> > 	-27.9705% +/- 0.0149878%
> > 	(Student's t, pooled s = 58864.4)
> 
> Thanks for sharing these results, but I wonder if this will capture
> regressions from locking changes (e.g. a lock being preemtible)? IIUC
> this is counting the instructions executed in these paths, and that
> won't change if the task gets preempted. Lock contention may be captured
> as extra instructions, but I am not sure we'll directly see its effect
> in terms of serialization and delays.

Yeah..

> I think we also need some high level testing (e.g. concurrent
> swapins/swapouts) to find that out. I think that's what Kairui's testing
> covers.

I do a fair amount of high-level testing: heavy parallel (make -j36 and
parallel dd) workloads (multiple zram devices configuration - zram0 ext4,
zram1 writeback device, zram2 swap) w/ and w/o lockdep.  In addition I also
run these workloads under heavy memory pressure (a 4GB VM), when oom-killer
starts to run around with a pair of scissors.  But it's mostly regression
testing.