linux-kernel - Re: scheduler performance regression since v6.11

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Message-ID: <20250520193831.GB39944@noisy.programming.kicks-ass.net>
Date: Tue, 20 May 2025 21:38:31 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Dietmar Eggemann <dietmar.eggemann@....com>
Cc: Chris Mason <clm@...a.com>, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...nel.org>, vschneid@...hat.com,
	Juri Lelli <juri.lelli@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: scheduler performance regression since v6.11

On Tue, May 20, 2025 at 04:38:09PM +0200, Dietmar Eggemann wrote:

> 3840cbe24cf0 - sched: psi: fix bogus pressure spikes from aggregation race
> 
> With CONFIG_PSI enabled we call cpu_clock(cpu) now multiple times (up to
> 4 times per task switch in my setup) in:
> 
> __schedule() -> psi_sched_switch() -> psi_task_switch() ->
> psi_group_change().
> 
> There seems to be another/other v6.12 related patch(es) later which
> cause(s) another 4% regression I yet have to discover.

Urgh, let me add this to the pile to look at. Thanks!