linux-kernel - Re: [PATCH] sched/nohz: Fix NOHZ imbalance by adding options for ILB CPU

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Message-ID: <CAKfTPtB3cyaYDPdCWjdPAsWcKTZCxw5rbWsS+AZ2sD8_FhgDhg@mail.gmail.com>
Date: Thu, 11 Sep 2025 10:55:21 +0200
From: Vincent Guittot <vincent.guittot@...aro.org>
To: "Christoph Lameter (Ampere)" <cl@...two.org>
Cc: Valentin Schneider <vschneid@...hat.com>, Adam Li <adamli@...amperecomputing.com>, mingo@...hat.com, 
	peterz@...radead.org, juri.lelli@...hat.com, dietmar.eggemann@....com, 
	rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de, frederic@...nel.org, 
	linux-kernel@...r.kernel.org, patches@...erecomputing.com
Subject: Re: [PATCH] sched/nohz: Fix NOHZ imbalance by adding options for ILB CPU

On Wed, 3 Sept 2025 at 22:44, Christoph Lameter (Ampere) <cl@...two.org> wrote:
>
> On Wed, 3 Sep 2025, Vincent Guittot wrote:
>
> > > AFAICT we have (at least) two options:
> > > 1) Trigger NOHZ balancing on a busy housekeeping CPU (what this patch does)
>
>
> Isnt there a third option?
>
> 3) Trigger load balancing if on a NOHZ_FULL cpu and multiple processes are
> running on it.

If there are several threads on the NOHZ_FULL CPu then the CPU has its
tick firing which will trigger the busy load balance for this CPU

>
>