linux-kernel - Re: stable 6.6: commit "sched/cpufreq: Rework schedutil governor performance estimation' causes a regression

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Message-ID: <CAKfTPtAq_90WkSbL-vg8Uh46WNjzqVApjDHF+htgdNBApRFM-w@mail.gmail.com>
Date: Fri, 21 Nov 2025 08:22:07 +0100
From: Vincent Guittot <vincent.guittot@...aro.org>
To: Sergey Senozhatsky <senozhatsky@...omium.org>
Cc: Christian Loehle <christian.loehle@....com>, "Rafael J. Wysocki" <rafael@...nel.org>, 
	Viresh Kumar <viresh.kumar@...aro.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Yu-Che Cheng <giver@...gle.com>, Tomasz Figa <tfiga@...omium.org>, stable@...r.kernel.org, 
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Lukasz Luba <lukasz.luba@....com>, Dietmar Eggemann <dietmar.eggemann@....com>
Subject: Re: stable 6.6: commit "sched/cpufreq: Rework schedutil governor
 performance estimation' causes a regression

On Fri, 21 Nov 2025 at 08:03, Sergey Senozhatsky
<senozhatsky@...omium.org> wrote:
>
> On (25/11/21 12:55), Sergey Senozhatsky wrote:
> > Hi Christian,
> >
> > On (25/11/20 10:15), Christian Loehle wrote:
> > > On 11/20/25 04:45, Sergey Senozhatsky wrote:
> > > > Hi,
> > > >
> > > > We are observing a performance regression on one of our arm64 boards.
> > > > We tracked it down to the linux-6.6.y commit ada8d7fa0ad4 ("sched/cpufreq:
> > > > Rework schedutil governor performance estimation").
> > > >
> > > > UI speedometer benchmark:
> > > > w/commit: 395  +/-38
> > > > w/o commit:       439  +/-14
> > > >
> > >
> > > Hi Sergey,
> > > Would be nice to get some details. What board?
> >
> > It's an MT8196 chromebook.
> >
> > > What do the OPPs look like?
> >
> > How do I find that out?
> >
> > > Does this system use uclamp during the benchmark? How?
> >
> > How do I find that out?
> >
> > > Given how large the stddev given by speedometer (version 3?) itself is, can we get the
> > > stats of a few runs?
> >
> > v2.1
> >
> > w/o patch     w/ patch
> > 440 +/-30     406 +/-11
> > 440 +/-14     413 +/-16
> > 444 +/-12     403 +/-14
> > 442 +/-12     412 +/-15
> >
> > > Maybe traces of cpu_frequency for both w/ and w/o?
> >
> > trace-cmd record -e power:cpu_frequency attached.
> >
> > "base" is with ada8d7fa0ad4
> > "revert" is ada8d7fa0ad4 reverted.
>
> Am getting failed delivery notifications.  I guess attaching those as
> text files wasn't a good idea after all.  Vincent, Christian, did you
> receive that email?

Yes I received it