linux-kernel - Re: [PATCH 2/3] perf/core: introduce pmu_event_flags and PMUEF_READ_CPU

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Date:	Thu, 4 Aug 2016 10:23:43 -0700
From:	David Carrillo-Cisneros <davidcc@...gle.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	"x86@...nel.org" <x86@...nel.org>, Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andi Kleen <ak@...ux.intel.com>,
	Kan Liang <kan.liang@...el.com>, Paul Turner <pjt@...gle.com>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 2/3] perf/core: introduce pmu_event_flags and PMUEF_READ_CPU_PKG

>> 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.