Re: [PATCH 2/3] perf/core: introduce pmu_event_flags and PMUEF_READ_CPU_PKG

[David Carrillo-Cisneros]

On Thu, Aug 4, 2016 at 10:27 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> On Thu, Aug 04, 2016 at 10:23:43AM -0700, David Carrillo-Cisneros wrote:
>> >> Introduce the flag PMUEF_READ_CPU_PKG, useful for uncore events, that
>> >> allows a PMU to signal the generic perf code that an event is readable
>> >> on the current CPU if the event is:
>> >>   - active in a CPU in the same package as the current CPU (local CPU)
>> >
>> > Ok that I get..
>> >
>> >>   - not active but is attached to a CPU (i.e. event->cpu != -1) in the
>> >>   same package as the current CPU.
>> >
>> > but this, not so much. Why would you want to read an inactive counter?
>>
>> Uncore counters are active even if its event is not.
>
> Not in general they are not, and if they are (freerunning msr counters
> for example) we should not include the counts when the event is
> inactive.
>
True that. I conflated Intel CQM specific behavior with other uncore
(In CQM we want to read when the event is inactive). I'll fix that in
next version.