Re: [PATCH] perf/x86/intel: Drop kernel samples even though :u is specified

[Jin, Yao]

On 5/19/2017 8:10 PM, Peter Zijlstra wrote:
> On Fri, May 19, 2017 at 08:06:09PM +0800, Jin, Yao wrote:
> > SNIP
> >
> > > I would much rather see this in generic code, somewhere around
> > > __perf_event_overflow() I suppose. That would retain proper accounting
> > > for the interrupt rate etc..
> > >
> > > Also it would work for all architectures. Because I'm thinking more than
> > > just x86 will suffer from skid.
> > Yes, moving to generic code is better.  Thanks for the suggestion! I will do
> > that.
> >
> > > If you're really worried, I suppose you can put it behind a PERF_PMU_CAP
> > > flag or something.
> > I guess what you are suggesting is to add checking like:
> >
> > if (is_sampling_event(event)) {
> >      if (event->pmu->capabilities & PERF_PMU_CAP_NO_INTERRUPT) {
> >          return;
> >      }
> > }
> Ah, I was more thinking of something like PERF_PMU_CAP_NO_SKID or
> something that would skip the test and preserve current behaviour.

OK, I understand now. For example, for PEBS event, its capabilities 
should be set with PERF_PMU_CAP_NO_SKID.

If the event's capabilities is set with PERF_PMU_CAP_NO_SKID, it should 
skip the checking and keep current behavior.

Thanks
Jin Yao