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

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Date:	Tue, 25 Aug 2015 20:15:45 +0000
From:	"Liang, Kan" <kan.liang@...el.com>
To:	Stephane Eranian <eranian@...gle.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


> >> >
> >> 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.
> >

Hi Stephane,

I thought more about your suggestion regarding to create a unified
power PMU for all related events include RAPL and residency.
It looks we can benefit from a simple unified name, but it also
brings too much confusion.
  - cstate residency is the time of the core/socket in specific cstate.
     While RAPL event is the power core/socket which consumed.
     They have different concepts. 
  - cstate residency includes both per-core and per-socket events.
     RAPL events is only per-socket. So the CPU mask is different.
     It's very confused that the events in same PMU has different CPU mask.

So I think it should be better to use different PMUs for RAPL and residency.

What do you think?

Thanks,
Kan