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

[Ingo Molnar <mingo@kernel.org>]

* Arnaldo Carvalho de Melo <acme@kernel.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