linux-kernel - [GIT PULL] scheduler fixes

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Date: Thu, 11 Jan 2024 12:09:23 +0100
From: Ingo Molnar <mingo@...nel.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Vincent Guittot <vincent.guittot@...aro.org>,
	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: [GIT PULL] scheduler fixes


* Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> 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.

Thanks a lot for bisecting this, and ack on the revert in any case, these 
are relatively fresh changes that clearly didn't get enough testing - sorry!

I also made the revert in sched/urgent & added a changelog, which you can 
pull from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git sched-urgent-2024-01-11

   # HEAD: 250ce3c1169743f3575cc5937fccd72380052795 Revert "sched/cpufreq: Rework schedutil governor performance estimation" and dependent commits

Revert recent changes to the sched_util logic, to address a bad
performance regression that increased kernel build time on Linus's
64-CPU desktop system substantially.

Lightly build and boot tested.

 Thanks,

	Ingo

------------------>
Ingo Molnar (1):
      Revert "sched/cpufreq: Rework schedutil governor performance estimation" and dependent commits


 include/linux/energy_model.h     |  1 +
 kernel/sched/core.c              | 90 +++++++++++++++++++++++-----------------
 kernel/sched/cpufreq_schedutil.c | 90 ++++++++++++----------------------------
 kernel/sched/fair.c              | 22 ++--------
 kernel/sched/sched.h             | 84 +++++++++++++++++++++++++++++++++----
 5 files changed, 160 insertions(+), 127 deletions(-)