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

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Message-ID: <86d759a5-9a96-49ff-9f75-8b56e2626d65@arm.com>
Date: Thu, 20 Nov 2025 10:15:11 +0000
From: Christian Loehle <christian.loehle@....com>
To: Sergey Senozhatsky <senozhatsky@...omium.org>,
 Vincent Guittot <vincent.guittot@...aro.org>,
 "Rafael J. Wysocki" <rafael@...nel.org>
Cc: 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 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? What do the OPPs look like?
Does this system use uclamp during the benchmark? How?
Given how large the stddev given by speedometer (version 3?) itself is, can we get the
stats of a few runs?
Maybe traces of cpu_frequency for both w/ and w/o?