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

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Message-ID: <ZZ+185pB84Ihovve@gmail.com>
Date: Thu, 11 Jan 2024 10:33:39 +0100
From: Ingo Molnar <mingo@...nel.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	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


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

> On Mon, 8 Jan 2024 at 06:07, Ingo Molnar <mingo@...nel.org> wrote:
> >
> > Please pull the latest sched/core git tree from:
> >
> >    git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git sched-core-2024-01-08
> 
> Just a note that I'm currently bisecting into this merge for a
> horrendous performance regression.
> 
> It makes my empty kernel build go from 22 seconds to 44 seconds, and
> makes a full kernel build enormously slower too.

Ouch, that's horrible ...

> I haven't finished the bisection, but it's now inside *just* this
> pull, so I can already tell that I'm going to revert something in
> here, because this has been making my merge window miserable.

Just as a quick test, does switching to the 'performance' governor work 
around the regression:

  for ((cpu=0; cpu < $(nproc); cpu++)); do echo performance > /sys/devices/system/cpu/cpu$cpu/cpufreq/scaling_governor; done

Thanks,

	Ingo