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

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Message-ID: <37D7C6CF3E00A74B8858931C1DB2F077018F4B39@SHSMSX103.ccr.corp.intel.com>
Date:	Fri, 28 Aug 2015 15:00:47 +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



> On Tue, Aug 25, 2015 at 1:15 PM, Liang, Kan <kan.liang@...el.com> wrote:
> >
> >> >> >
> >> >> 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?
> >
> Well, you are maybe confusing events with PMU. If you look at the core
> PMU, it cover many events measuring vastly different aspects of the core.
> Some events are per-thread, others are per-core.
> 
> Here, I was thinking it would be good to have some power// PMU with
> many events covering cstate residency, energy consumption. And yes,
> some events would be per-socket, others per-core.

So you agree to create two new cstate PMUs (per-core and per-socket) to
cover cstate residency?
If so, I will start to implement the V3 version for two new PMUs. 

Thanks,
Kan