Messages in this thread | | | From | Stephane Eranian <> | Date | Tue, 30 Jan 2018 11:56:33 -0800 | Subject | Re: [PATCH V3 0/5] bugs fix for large PEBS mmap read and rdpmc read |
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On Tue, Jan 30, 2018 at 10:52 AM, Jiri Olsa <jolsa@redhat.com> wrote: > > On Tue, Jan 30, 2018 at 11:48:18AM -0500, Liang, Kan wrote: > > SNIP > > > > > > > > > The events in fixed mode could enable large PEBS. Events in freq mode should > > > > not enable large PEBS. > > > > I think that could be a problem if some events try to enable large PEBS, > > > > while others not. > > > > > > > You only enable large PEBS if 100% of the events use fixed periods, > > > either via -c period > > > or because they all use individual period=p. The --no-period could > > > also be used to remove > > > the period for measurements where the period is not needed. > > > > > > Oh, right, the kernel has already guaranteed that. > > if (cpuc->n_pebs == cpuc->n_large_pebs) { > > threshold = ds->pebs_absolute_maximum - > > x86_pmu.max_pebs_events * x86_pmu.pebs_record_size; > > } else { > > > > Sorry for the noise. > > > > jirka's patch looks good to me. > > cool, I'll post it later this week > Still, the part I am missing here, is why asking for PERF_SAMPLE_PERIOD voids large PEBS.
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