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

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Date:	Fri, 28 Aug 2015 07:53:59 -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 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.
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