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

From: Stephane Eranian
Date: Fri Aug 28 2015 - 10:54:05 EST

On Tue, Aug 25, 2015 at 1:15 PM, Liang, Kan <kan.liang@xxxxxxxxx> 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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