Messages in this thread | | | Date | Thu, 18 Jan 2018 10:49:48 +0100 | From | Jiri Olsa <> | Subject | Re: [RESEND PATCH V2 3/4] perf/x86/intel: drain PEBS buffer in event read |
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On Tue, Jan 16, 2018 at 01:49:13PM -0500, Liang, Kan wrote: > > > On 1/11/2018 10:45 AM, Jiri Olsa wrote: > > On Thu, Jan 11, 2018 at 10:21:25AM -0500, Liang, Kan wrote: > > > > SNIP > > > > > > > > > > hum, but the PEBS drain is specific just for > > > > PERF_X86_EVENT_AUTO_RELOAD events, right? > > > > > > Accurately, PEBS drain is specific for PERF_X86_EVENT_FREERUNNING here. > > > PERF_X86_EVENT_FREERUNNING event must be _AUTO_RELOAD event. > > > But in some cases, _AUTO_RELOAD event cannot be _FREERUNNING event. > > > > > > Only the event which is both _FREERUNNING and _AUTO_RELOAD need to do PEBS > > > drain in _read(). > > > > > > So it does the check in intel_pmu_pebs_read() > > > + if (pebs_needs_sched_cb(cpuc)) > > > + return intel_pmu_drain_pebs_buffer(); > > > > > > > > > > > wrt readability maybe you could add function like: > > > > > > The existing function pebs_needs_sched_cb() can do the check. > > > We just need to expose it, and also the intel_pmu_drain_pebs_buffer(). > > > > > > But to be honest, I still cannot see a reason for that. > > > It could save a call to intel_pmu_pebs_read(), but _read() is not critical > > > path. It doesn't save much. > > > > hum, pmu->read is also called for PERF_SAMPLE_READ for sample, > > check perf_output_read > > > > for non sampling event you shouldn't be able to create PEBS > > event, there's check in x86_pmu_hw_config > > > > I agree it does not save much, it just confused me while > > I was reading the code, like why is this needed for all > > events with precise_ip > > > > > Sorry for the late response. > > How about the patch as below? > The patch will be split into two patches in V3. One is to introduce > intel_pmu_large_pebs_read, the other is to introduce intel_pmu_read_event. > > Thanks, > Kan > > diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c > index 731153a..1610a9d 100644 > --- a/arch/x86/events/intel/core.c > +++ b/arch/x86/events/intel/core.c > @@ -2060,6 +2060,14 @@ static void intel_pmu_del_event(struct perf_event > *event) > intel_pmu_pebs_del(event); > } > > +static void intel_pmu_read_event(struct perf_event *event) > +{ > + if (intel_pmu_large_pebs_read(event)) > + return;
should this be 'if (!intel_pmu_large_pebs_read(event))'
but looks better for me without the precise_ip check
thanks, jirka
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