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

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Date:	Thu, 6 Aug 2015 18:52:35 +0000
From:	"Liang, Kan" <kan.liang@...el.com>
To:	Stephane Eranian <eranian@...gle.com>,
	Peter Zijlstra <peterz@...radead.org>
CC:	"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



> >> +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.

> >
> 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