linux-kernel - Re: [PATCH] sched/fair: Optimize CPU iteration using for_each_cpu

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Message-ID: <xhsmhwm6zh6wr.mognet@vschneid-thinkpadt14sgen2i.remote.csb>
Date: Tue, 19 Aug 2025 13:45:08 +0200
From: Valentin Schneider <vschneid@...hat.com>
To: lirongqing <lirongqing@...du.com>, mingo@...hat.com,
 peterz@...radead.org, juri.lelli@...hat.com, vincent.guittot@...aro.org,
 dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
 mgorman@...e.de, linux-kernel@...r.kernel.org
Cc: Li RongQing <lirongqing@...du.com>
Subject: Re: [PATCH] sched/fair: Optimize CPU iteration using
 for_each_cpu_and[not]

On 15/08/25 09:15, lirongqing wrote:
> From: Li RongQing <lirongqing@...du.com>
>
> Replace open-coded CPU iteration patterns with more efficient
> for_each_cpu_and() and for_each_cpu_andnot() macros in three locations.
>
> This change both simplifies the code and provides minor performance
> improvements by using the more specialized iteration macros.
>

TBF I'm not sure it does improve anything for the SMT cases considering we
don't see much more than SMT8.

The task_numa_find_cpu() one I do agree makes things better.

> Signed-off-by: Li RongQing <lirongqing@...du.com>

Reviewed-by: Valentin Schneider <vschneid@...hat.com>