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

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Message-ID: <2ktr5znjidilpxm2ycixunqlmhu253xwov4tpnb2qablrsqmbv@ysacm5nbcjw7>
Date: Fri, 21 Nov 2025 12:55:16 +0900
From: Sergey Senozhatsky <senozhatsky@...omium.org>
To: Christian Loehle <christian.loehle@....com>
Cc: Sergey Senozhatsky <senozhatsky@...omium.org>, 
	Vincent Guittot <vincent.guittot@...aro.org>, "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

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.

View attachment "cpu_frequency-trace-base.txt" of type "text/plain" (4875973 bytes)

View attachment "cpu_frequency-trace-revert.txt" of type "text/plain" (5553926 bytes)