linux-kernel - Re: [PATCH v14 7/7] timers: Exclude isolated cpus from timer migration

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Message-ID: <f47a6827fa07db12581d2a6b8c1cfe1ce467aa21.camel@redhat.com>
Date: Mon, 10 Nov 2025 14:06:08 +0100
From: Gabriele Monaco <gmonaco@...hat.com>
To: linux-kernel@...r.kernel.org, Anna-Maria Behnsen
 <anna-maria@...utronix.de>,  Frederic Weisbecker	 <frederic@...nel.org>,
 Thomas Gleixner <tglx@...utronix.de>, Waiman Long	 <llong@...hat.com>
Cc: "John B . Wyatt IV" <jwyatt@...hat.com>, "John B . Wyatt IV"
	 <sageofredondo@...il.com>
Subject: Re: [PATCH v14 7/7] timers: Exclude isolated cpus from timer
 migration

On Tue, 2025-11-04 at 11:47 +0100, 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 non isolated and online;
> 
> ...
> 
> +/* Enabled during late initcall */
> +DEFINE_STATIC_KEY_FALSE(tmigr_exclude_isolated);
> +

I forgot to mark this as static:

+static DEFINE_STATIC_KEY_FALSE(tmigr_exclude_isolated);

will send a new version after getting a review/comments.

Frederic, Thomas, besides that, does this series look ready to you?

Thanks,
Gabriele