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

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Date:	Fri, 28 Aug 2015 15:16:23 +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 Fri, Aug 28, 2015 at 8:00 AM, Liang, Kan <kan.liang@...el.com> wrote:
> >
> >
> >> 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.
> >
> I did not say that. Instead I said there is some benefits in having everything
> under a power// PMU, including possibly portability to other non x86
> architectures.

But the events in power// PMU will be per-socket or per-core.
How should we handle it?
What should we show in cpumask?