Re: [RFC] perf/x86/intel: Account interrupts for PEBS errors

From: Jiri Olsa
Date: Thu Dec 15 2016 - 02:15:39 EST


On Wed, Dec 14, 2016 at 08:32:39PM +0100, Peter Zijlstra wrote:
> On Wed, Dec 14, 2016 at 07:16:36PM +0100, Jiri Olsa wrote:
>
> > > > +++ b/arch/x86/events/intel/ds.c
> > > > @@ -1389,9 +1389,13 @@ static void intel_pmu_drain_pebs_nhm(struct pt_regs *iregs)
> > > > continue;
> > > >
> > > > /* log dropped samples number */
> > > > - if (error[bit])
> > > > + if (error[bit]) {
> > > > perf_log_lost_samples(event, error[bit]);
> > > >
> > > > + if (perf_event_account_interrupt(event, 1))
> > >
> > > Seems a bit daft to expose the .throttle argument, since that would be
> > > the only point of calling this.
> >
> > there's also the other caller from __perf_event_overflow
>
> See the below patchlet ;-)

ok, np ;-)

>
> > > > +static int __perf_event_overflow(struct perf_event *event,
> > > > + int throttle, struct perf_sample_data *data,
> > > > + struct pt_regs *regs)
> > > > +{
> > > > + int events = atomic_read(&event->event_limit);
> > > > + struct hw_perf_event *hwc = &event->hw;
> > > > + int ret = 0;
> > > > +
> > > > + /*
> > > > + * Non-sampling counters might still use the PMI to fold short
> > > > + * hardware counters, ignore those.
> > > > + */
> > > > + if (unlikely(!is_sampling_event(event)))
> > > > + return 0;
> > > > +
> > > > + ret = perf_event_account_interrupt(event, throttle);
> > > > +
> > > > if (event->attr.freq) {
> > > > u64 now = perf_clock();
> > > > s64 delta = now - hwc->freq_time_stamp;
> > >
> > > Arguably, everything in __perf_event_overflow() except for calling of
> > > ->overflow_handler() should be done I think.
> >
> > well, I was wondering about that period adjustment bit
> >
> > but I wasn't sure about those pending_kill/pending_wakeup bits,
> > they make sense to me only if we have some data to deliver
>
> Hmm, maybe. Please add a comment, that way we can at least rediscover we
> thought about this.

ook

jirka