linux-kernel - Re: [PATCH] sched/fair: Fix frequency selection for non invariant case

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Date: Thu, 15 Feb 2024 09:45:01 +0100
From: Thorsten Leemhuis <regressions@...mhuis.info>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Jon Hunter <jonathanh@...dia.com>, mingo@...hat.com,
 peterz@...radead.org, juri.lelli@...hat.com, dietmar.eggemann@....com,
 rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
 bristot@...hat.com, vschneid@...hat.com, wkarny@...il.com,
 qyousef@...alina.io, tglx@...utronix.de, rafael@...nel.org,
 viresh.kumar@...aro.org, linux-kernel@...r.kernel.org,
 linux-pm@...r.kernel.org,
 "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
 Thierry Reding <treding@...dia.com>, Sasha Levin <sashal@...dia.com>,
 Laxman Dewangan <ldewangan@...dia.com>,
 Shardar Mohammed <smohammed@...dia.com>,
 Vincent Guittot <vincent.guittot@...aro.org>,
 Linux kernel regressions list <regressions@...ts.linux.dev>
Subject: Re: [PATCH] sched/fair: Fix frequency selection for non invariant
 case

Linus, what...

On 14.02.24 18:22, Vincent Guittot wrote:
> On Wed, 14 Feb 2024 at 18:20, Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
>> On Wed, 14 Feb 2024 at 09:12, Jon Hunter <jonathanh@...dia.com> wrote:
>>> We have also observed a performance degradation on our Tegra platforms
>>> with v6.8-rc1. Unfortunately, the above change does not fix the problem
>>> for us and we are still seeing a performance issue with v6.8-rc4. For
>>> example, running Dhrystone on Tegra234 I am seeing the following ...
>>> [...]
>>> If I revert this change and the following ...
>>>   b3edde44e5d4 ("cpufreq/schedutil: Use a fixed reference frequency")
>>>   f12560779f9d ("sched/cpufreq: Rework iowait boost")
>>>   9c0b4bb7f630 ("sched/cpufreq: Rework schedutil governor
>>> ... then the perf is similar to where it was ...
>>
>> Ok, guys, this whole scheduler / cpufreq rewrite seems to have been
>> completely buggered.
>> [...]
> This should fix it:
> https://lore.kernel.org/lkml/20240117190545.596057-1-vincent.guittot@linaro.org/

..do you want me to do in situations like this? I'm asking, as I see
situations like this frequently -- e.g. people reporting problems a
second, third, or fourth time while the fix is already sitting in -next
for a few days.

Want me to list them in the weekly reports so that you can cherry-pick
them from -next if you want?

Ciao, Thorsten