On Thu, Jun 01, 2023 at 06:23:21AM +0200, Lukáš Doktor wrote: > Dne 31. 05. 23 v 19:14 Stefan Hajnoczi napsal(a): > > On Wed, 31 May 2023 at 12:50, Lukáš Doktor <ldok...@redhat.com> wrote: > >> > >> Dne 26. 05. 23 v 12:56 Stefan Hajnoczi napsal(a): > >>> On Fri, 26 May 2023 at 04:07, Lukáš Doktor <ldok...@redhat.com> wrote: > >>>> > >>>> Dne 25. 05. 23 v 17:21 Stefan Hajnoczi napsal(a): > >>>>> On Thu, 25 May 2023 at 06:18, Lukáš Doktor <ldok...@redhat.com> wrote: > >>>>>> the perf-ci detected and bisected the 6d740fb - aio-posix: do not nest > >>>>>> poll handlers - as a performance improvement when using multiple > >>>>>> concurrent jobs and 4k (22%) as well as 1024k (63%) blocks on aarch64 > >>>>>> (on a slow rotational disk). > >>>>>> > >>>>>> > >>>>>> https://ldoktor.github.io/tmp/RedHat-virtlab-arm09/v8.0.0/150-improvement.html > >>>>>> > >>>>>> Based on the commit message I guess it's expected so take this just as > >>>>>> a record of an improvement. > >>>>> > >>>>> The commit was not intended to change performance and I'm not sure why > >>>>> it happens! > >>>>> > >>>> > >>>> It had and today the x86_64 pipeline finished which shows similar > >>>> improvement just not in read but rather in write instead and only for 4k > >>>> blocks (~40%). For 1024k blocks I can see it scoring a bit better > >>>> (~1.5%). Reads are too jittery to really tell anything on that machine. > >>>> Anyway I have not done any thorough testing, just a bisection with the > >>>> most significant setting. > >>>> > >>>> From around the same time I can see a NVMe regression in 4k writes, but > >>>> first bisection job showed nothing. I'll increase the range and try > >>>> again as each job since that day shows similar drop. > >>> > >> > >> Hello Stefan, folks, > >> > >> the regression proved to be there and stably reproducible. With NVMe 4k > >> writes with jobs=10 and iodepth=4 I can see a 50% regression on my machine: > >> > >> > >> https://ldoktor.github.io/tmp/RedHat-virtlab722/v8.0.0/150-regression.html > >> > >> The rest of the cases doesn't show any change at all. I can provide more > >> data if someone is interested. > > > > Which commit caused the regression? > > Hello Stefan, > > the same one that caused the improvement on rotational disks: > 6d740fb01b9f0f5ea7a82f4d5e458d91940a19ee
Thanks. This commit definitely needs more investigation. I didn't expect it to have a noticeable effect. I will take a look in July. Stefan
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