linux-kernel - RE: [PATCH V2 1/1] perf/core: don't find side-band event from all pmus

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Date:	Thu, 31 Mar 2016 14:05:46 +0000
From:	"Liang, Kan" <kan.liang@...el.com>
To:	"acme@...nel.org" <acme@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>
CC:	"ak@...ux.intel.com" <ak@...ux.intel.com>,
	"eranian@...gle.com" <eranian@...gle.com>,
	"vincent.weaver@...ne.edu" <vincent.weaver@...ne.edu>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"mingo@...nel.org" <mingo@...nel.org>,
	"acme@...hat.com" <acme@...hat.com>,
	"jolsa@...hat.com" <jolsa@...hat.com>,
	"alexander.shishkin@...ux.intel.com" 
	<alexander.shishkin@...ux.intel.com>,
	"ying.huang@...ux.intel.com" <ying.huang@...ux.intel.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH V2 1/1] perf/core: don't find side-band event from all
 pmus



> > +static void perf_event_sb_mask(unsigned int sb_mask,
> > +			       perf_event_aux_output_cb output,
> > +			       void *data)
> > +{
> > +	int sb;
> > +
> > +	for (sb = 0; sb < sb_nr; sb++) {
> > +		if (!(sb_mask & (1 << sb)))
> > +			continue;
> > +		perf_event_sb_iterate(sb, output, data);
> > +	}
> > +}
> 
> > @@ -5852,7 +5910,8 @@ static void perf_event_task(struct task_struct
> > *task,
> >
> >  	perf_event_aux(perf_event_task_output,
> >  		       &task_event,
> > -		       task_ctx);
> > +		       task_ctx,
> > +		       (1 << sb_task) | (1 << sb_mmap) | (1 << sb_comm));
> >  }
> 
> So one side-effect of this change is that the above event can be delivered
> 3 times if you're 'lucky'.
> 
> Acme; does userspace care?

Hi Arnaldo,

Do you think if it's an issue for userspace?

Thanks,
Kan