linux-kernel - Re: [perf stat] Extend --cpu to non-system-wide runs too? was Re: [PATCH v3] perf bench sched pipe: Add -G/--cgroups option

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Message-ID: <ZS6BgfOUeWQnI1mS@gmail.com>
Date:   Tue, 17 Oct 2023 14:43:45 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Namhyung Kim <namhyung@...nel.org>, Jiri Olsa <jolsa@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-perf-users@...r.kernel.org
Subject: Re: [perf stat] Extend --cpu to non-system-wide runs too? was Re:
 [PATCH v3] perf bench sched pipe: Add -G/--cgroups option


* Arnaldo Carvalho de Melo <acme@...nel.org> wrote:

> Em Tue, Oct 17, 2023 at 01:40:07PM +0200, Ingo Molnar escreveu:
> > Side note: it might make sense to add a sane cpumask/affinity setting 
> > option to perf stat itself:
> > 
> >   perf stat --cpumask 
> > 
> > ... or so?
> > 
> > We do have -C:
> > 
> >     -C, --cpu <cpu>       list of cpus to monitor in system-wide
> > 
> > ... but that's limited to --all-cpus, right?
> > 
> > Perhaps we could extend --cpu to non-system-wide runs too?
> 
> Maybe I misunderstood your question, but its a list of cpus to limit the
> counting:

Ok.

So I thought that "--cpumask mask/list/etc" should simply do what 'taskset' 
is doing: using the sched_setaffinity() syscall to make the current 
workload and all its children.

There's impact on perf stat itself: it could just call sched_setaffinity() 
early on, and not bother about it?

Having it built-in into perf would simply make it easier to not forget 
running 'taskset'. :-)

Thanks,

	Ingo