linux-kernel - Re: [PATCH v2 2/2] sched/topology: Optimize topology_span

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Message-ID: <xhsmhr0f69767.mognet@vschneid-thinkpadt14sgen2i.remote.csb>
Date: Mon, 15 Apr 2024 13:50:08 +0200
From: Valentin Schneider <vschneid@...hat.com>
To: Kyle Meyer <kyle.meyer@....com>, linux-kernel@...r.kernel.org,
 yury.norov@...il.com, andriy.shevchenko@...ux.intel.com,
 linux@...musvillemoes.dk, 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, bristot@...hat.com
Cc: russ.anderson@....com, dimitri.sivanich@....com, steve.wahl@....com,
 Kyle Meyer <kyle.meyer@....com>
Subject: Re: [PATCH v2 2/2] sched/topology: Optimize topology_span_sane()

On 10/04/24 16:33, Kyle Meyer wrote:
> Optimize topology_span_sane() by removing duplicate comparisons.
>
> Since topology_span_sane() is called inside of for_each_cpu(), each
> pervious CPU has already been compared against every other CPU. The
> current CPU only needs to be compared against higher-numbered CPUs.
>
> The total number of comparisons is reduced from N * (N - 1) to
> N * (N - 1) / 2 on each non-NUMA scheduling domain level.
>
> Signed-off-by: Kyle Meyer <kyle.meyer@....com>
> Reviewed-by: Yury Norov <yury.norov@...il.com>
> Acked-by: Vincent Guittot <vincent.guittot@...aro.org>

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