linux-kernel - Re: [PATCH v4] sched/core: Use zero length to reset cpumasks in sched

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Message-ID: <871qeaefco.fsf@oldenburg.str.redhat.com>
Date:   Wed, 04 Oct 2023 14:34:15 +0200
From:   Florian Weimer <fweimer@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Waiman Long <longman@...hat.com>, Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>,
        linux-kernel@...r.kernel.org, Phil Auld <pauld@...hat.com>,
        Brent Rowsell <browsell@...hat.com>,
        Peter Hunt <pehunt@...hat.com>
Subject: Re: [PATCH v4] sched/core: Use zero length to reset cpumasks in
 sched_setaffinity()

* Peter Zijlstra:

> Subject: sched: Add CPU_FILL()
>
> Add the CPU_FILL() macros to easily create an all-set cpumask.
>
> FreeBSD also provides this macro with this semantic.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>

My main concer is that obtaining the size of the mask, or at least an
approximiation is not exactly easy.  If there's an expectation that
applications reset the mask more often than they do today (I don't have
the full context here), then we'd some decent interface to get the
approriate size.

Thanks,
Florian