Re: [PATCH v2] perf/core: Add support for PMUs that can be read from more than 1 CPU

[Saravana Kannan]

On 03/05/2018 04:21 AM, Mark Rutland wrote:
> On Mon, Mar 05, 2018 at 12:17:02PM +0000, Mark Rutland wrote:
> > On Fri, Mar 02, 2018 at 05:14:53PM -0800, Saravana Kannan wrote:
>
> > > @@ -629,6 +629,7 @@ struct perf_event {
> > >
> > >   	int				oncpu;
> > >   	int				cpu;
> > > +	cpumask_t			readable_on_cpus;
> >
> > For most PMUs, this will be emptry, and it's potentially *very* large
> > (e.g. on systems where NR_CPUS is 4096). Please use a poitner to a mask,
> > as I suggested in [1], e.g.
>
> > [1] https://lkml.kernel.org/r/20171128124534.3jvuala525wvn64r@xxxxxxxxxxxxxxxxxxxxxx
>
> Whoops, that should've been:
>
> [1] https://lkml.kernel.org/r/20180225143802.denbkubqjg2dc7af@salmiak

I didn't notice you mentioned the use of pointers, but I was planning on 
doing that anyway. But then I realize people will complain about 
cacheline bouncing across 4096 CPUs if I use a cpu mask pointer.

Thanks,
Saravana

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