Re: [RESEND PATCH V2 3/4] perf/x86/intel: drain PEBS buffer in event read

[Liang, Kan]

On 1/10/2018 5:39 AM, Jiri Olsa wrote:
> On Mon, Jan 08, 2018 at 07:15:15AM -0800, kan.liang@xxxxxxxxx wrote:
> > From: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
> >
> > When the PEBS interrupt threshold is larger than one, there is no way to
> > get exact auto-reload times and value needed for event update unless
> > flush the PEBS buffer.
> >
> > Drain the PEBS buffer in event read when large PEBS is enabled.
> >
> > For the threshold is one, even auto-reload is enabled, it doesn't need
> > to be specially handled. Because auto-reload is only effect when event
> > overflow. There is no overflow in event read.
> >
> > Signed-off-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
> > ---
> >   arch/x86/events/intel/core.c |  9 +++++++++
> >   arch/x86/events/intel/ds.c   | 10 ++++++++++
> >   arch/x86/events/perf_event.h |  2 ++
> >   3 files changed, 21 insertions(+)
> >
> > diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
> > index 09c26a4..bdc35f8 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 (event->attr.precise_ip)
> > +		return intel_pmu_pebs_read(event);
>
> check for (event->hw.flags & PERF_X86_EVENT_AUTO_RELOAD)
> would be more accurate?

It will narrow down the events.
But considering the readability, I think it would be better to use 
precise_ip.The exposed functions in ds.c should be generic functions for 
all PEBS events, not specific case.
I think _AUTO_RELOAD looks too specific.

Thanks,
Kan