linux-kernel - Re: [patch V3 06/20] sched/mmcid: Prevent pointless work in mm_update_cpus

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Message-ID: <9c0c4bef-1b56-49db-b9cc-953e26572fd6@efficios.com>
Date: Wed, 29 Oct 2025 11:45:21 -0400
From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To: Thomas Gleixner <tglx@...utronix.de>, LKML <linux-kernel@...r.kernel.org>
Cc: Peter Zijlstra <peterz@...radead.org>,
 Gabriele Monaco <gmonaco@...hat.com>, Michael Jeanson
 <mjeanson@...icios.com>, Jens Axboe <axboe@...nel.dk>,
 "Paul E. McKenney" <paulmck@...nel.org>,
 "Gautham R. Shenoy" <gautham.shenoy@....com>,
 Florian Weimer <fweimer@...hat.com>, Tim Chen <tim.c.chen@...el.com>,
 Yury Norov <yury.norov@...il.com>, Shrikanth Hegde <sshegde@...ux.ibm.com>
Subject: Re: [patch V3 06/20] sched/mmcid: Prevent pointless work in
 mm_update_cpus_allowed()

On 2025-10-29 09:09, Thomas Gleixner wrote:
> mm_update_cpus_allowed() is not required to be invoked for affinity changes
> due to migrate_disable() and migrate_enable().
> 
> migrate_disable() restricts the task temporarily to a CPU on which the task
> was already allowed to run, so nothing changes. migrate_enable() restores
> the actual task affinity mask.
> 
> If that mask changed between migrate_disable() and migrate_enable() then
> that change was already accounted for.
> 
> Move the invocation to the proper place to avoid that.

Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>

-- 
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com