linux-kernel - Re: [PATCH v6 0/6] timers: Exclude isolated cpus from timer migation

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Message-ID: <aFKvc6FK9CH5BsNH@localhost.localdomain>
Date: Wed, 18 Jun 2025 14:22:11 +0200
From: Frederic Weisbecker <frederic@...nel.org>
To: Gabriele Monaco <gmonaco@...hat.com>
Cc: linux-kernel@...r.kernel.org,
	Anna-Maria Behnsen <anna-maria@...utronix.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Waiman Long <longman@...hat.com>
Subject: Re: [PATCH v6 0/6] timers: Exclude isolated cpus from timer migation

Hi Gabriele,

Le Wed, Jun 18, 2025 at 02:17:29PM +0200, Gabriele Monaco a écrit :
> On Fri, 2025-05-30 at 16:20 +0200, Gabriele Monaco wrote:
> > The timer migration mechanism allows active CPUs to pull timers from
> > idle ones to improve the overall idle time. This is however undesired
> > when CPU intensive workloads run on isolated cores, as the algorithm
> > would move the timers from housekeeping to isolated cores, negatively
> > affecting the isolation.
> > 
> > [...]
> > 
> > Exclude isolated cores from the timer migration algorithm, extend the
> > concept of unavailable cores, currently used for offline ones, to
> > isolated ones:
> > * A core is unavailable if isolated or offline;
> > * A core is available if isolated and offline;
> > 
> > A core is considered unavailable as isolated if it belongs to:
> > * the isolcpus (domain) list
> > * an isolated cpuset
> > Except if it is:
> > * in the nohz_full list (already idle for the hierarchy)
> > * the nohz timekeeper core (must be available to handle global
> > timers)
> 
> Frederic, Thomas, Waiman, would you have time to review this series?
> Thanks,
> Gabriele

Yes, sorry I got distracted with other things (although quite related).
I will give it a priority soonish!

Thanks.

-- 
Frederic Weisbecker
SUSE Labs