From: Stefan Hajnoczi <stefanha@gmail.com>
To: "Lukáš Doktor" <ldoktor@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>,
qemu-devel <qemu-devel@nongnu.org>
Subject: Re: Performance improvement with 6d740fb01b9f0f5ea7a82f4d5e458d91940a19ee
Date: Wed, 31 May 2023 13:14:29 -0400 [thread overview]
Message-ID: <CAJSP0QUc504kE_zM7fb0NQLG49eK2prWJZm9o=S6SosYqntEZA@mail.gmail.com> (raw)
In-Reply-To: <3584ed8c-e60c-54bd-1abe-8294e985119a@redhat.com>
On Wed, 31 May 2023 at 12:50, Lukáš Doktor <ldoktor@redhat.com> wrote:
>
> Dne 26. 05. 23 v 12:56 Stefan Hajnoczi napsal(a):
> > On Fri, 26 May 2023 at 04:07, Lukáš Doktor <ldoktor@redhat.com> wrote:
> >>
> >> Dne 25. 05. 23 v 17:21 Stefan Hajnoczi napsal(a):
> >>> On Thu, 25 May 2023 at 06:18, Lukáš Doktor <ldoktor@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?
Stefan
next prev parent reply other threads:[~2023-05-31 17:14 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-25 10:18 Performance improvement with 6d740fb01b9f0f5ea7a82f4d5e458d91940a19ee Lukáš Doktor
2023-05-25 15:21 ` Stefan Hajnoczi
2023-05-26 8:06 ` Lukáš Doktor
2023-05-26 10:56 ` Stefan Hajnoczi
2023-05-31 16:50 ` Lukáš Doktor
2023-05-31 17:14 ` Stefan Hajnoczi [this message]
2023-06-01 4:23 ` Performance improvement and regression " Lukáš Doktor
2023-06-01 13:17 ` Stefan Hajnoczi
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