linux-kernel - Re: [GIT PULL] Scheduler changes for v6.8

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Message-ID: <CAHk-=wjK28MUqBZzBSMEM8vdJhDOuXGSWPmmp04GEt9CXtW6Pw@mail.gmail.com>
Date: Wed, 10 Jan 2024 14:57:14 -0800
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Ingo Molnar <mingo@...nel.org>, Vincent Guittot <vincent.guittot@...aro.org>
Cc: linux-kernel@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>, 
	Thomas Gleixner <tglx@...utronix.de>, Juri Lelli <juri.lelli@...hat.com>, 
	Dietmar Eggemann <dietmar.eggemann@....com>, Steven Rostedt <rostedt@...dmis.org>, 
	Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>, 
	Daniel Bristot de Oliveira <bristot@...hat.com>, Valentin Schneider <vschneid@...hat.com>
Subject: Re: [GIT PULL] Scheduler changes for v6.8

On Wed, 10 Jan 2024 at 14:41, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> It's one of these two:
>
>   f12560779f9d sched/cpufreq: Rework iowait boost
>   9c0b4bb7f630 sched/cpufreq: Rework schedutil governor performance estimation
>
> one more boot to go, then I'll try to revert whichever causes my
> machine to perform horribly much worse.

I guess it should come as no surprise that the result is

   9c0b4bb7f6303c9c4e2e34984c46f5a86478f84d is the first bad commit

but to revert cleanly I will have to revert all of

      b3edde44e5d4 ("cpufreq/schedutil: Use a fixed reference frequency")
      f12560779f9d ("sched/cpufreq: Rework iowait boost")
      9c0b4bb7f630 ("sched/cpufreq: Rework schedutil governor
performance estimation")

This is on a 32-core (64-thread) AMD Ryzen Threadripper 3970X, fwiw.

I'll keep that revert in my private test-tree for now (so that I have
a working machine again), but I'll move it to my main branch soon
unless somebody has a quick fix for this problem.

                Linus