linux-kernel - Re: [PATCH V2 1/1] perf/x86: Add Intel power cstate PMUs support

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Date:	Thu, 6 Aug 2015 12:20:37 -0700
From:	Stephane Eranian <eranian@...gle.com>
To:	"Liang, Kan" <kan.liang@...el.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	"mingo@...hat.com" <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	"ak@...ux.intel.com" <ak@...ux.intel.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V2 1/1] perf/x86: Add Intel power cstate PMUs support

On Thu, Aug 6, 2015 at 11:52 AM, Liang, Kan <kan.liang@...el.com> wrote:
>
>
>> >> +static cpumask_t power_cstate_core_cpu_mask;
>> >
>> > That one typically does not need a cpumask.
>> >
>> You need to pick one CPU out of the multi-core. But it is for client parts
>> thus there is only one socket. At least this is my understanding.
>>
>
> CORE_C*_RESIDENCY are available for physical processor core.
> So logical processor in same physical processor core share the same
> counter.
> I think we need the cpumask to identify the default logical processor which
> do counting.
>
Did you restrict these events to system-wide mode only?

>> >
>> I understand that these metrics are useful and needed however if I look at
>> the broader picture I see many PMUs doing similar things or appearing
>> different when they are actually very close. It would be nice to have a
>> more unified approach. You have RAPL (client, server) which appears as
>> the power PMU. You have the PCU uncore on servers which also provides
>> C-state residency info. Yet, all these appear differently and expose events
>> with different names.
>> I think we could benefit from a more unifie approach here such that you
>> would be able to do
>>
>> $    perf stat -a -e power/c6-residency/, power/energy-pkg/
>>
>> on client and server without having to change the pmu name of the event
>> names.
>
> Yes, I agree. I'll think about it.
>
> Thanks,
> Kan
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