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Date: Wed, 12 Aug 2009 14:22:25 +0200
Message-ID: <7c86c4470908120522m1eaf891bqb394df072dddc701@mail.gmail.com>
Subject: Re: perf_counters issue with PERF_SAMPLE_GROUP
From: stephane eranian <eranian@googlemail.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
       LKML <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@linux-foundation.org>,
       Thomas Gleixner <tglx@linutronix.de>,
       Robert Richter <robert.richter@amd.com>,
       Paul Mackerras <paulus@samba.org>, Andi Kleen <andi@firstfloor.org>,
       Maynard Johnson <mpjohn@us.ibm.com>, Carl Love <cel@us.ibm.com>,
       Corey J Ashford <cjashfor@us.ibm.com>,
       Philip Mucci <mucci@eecs.utk.edu>, Dan Terpstra <terpstra@eecs.utk.edu>,
       perfmon2-devel <perfmon2-devel@lists.sourceforge.net>
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On Wed, Aug 12, 2009 at 11:02 AM, Ingo Molnar<mingo@elte.hu> wrote:
>
> * Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
>
>> On Tue, 2009-08-11 at 23:08 +0200, stephane eranian wrote:
>>
>> > But aren't you going to change the cpu, pid target stuff we
>> > discussed a couple of weeks ago anyway?
>>
>> Right, I'd like to, but Ingo doesn't. I haven't heard back from
>> Paul on this.
>
> Not sure we want to change it. Mixing PID and CPU into the same
> space disallows the simultaneous application of both. I.e. right now
> we allow 3 models:
>
>  - PID-ish
>  - CPU-ish
>  - PID and CPU [say measure CPU#2 component of an inherited workload.]
>
How useful is that last model, especially why only one CPU?

> Also, i dont really see the use-cases for new targets. (i've seen a
> few mentioned but none seemed valid) What new targets do people have
> in mind?

I seem to recall people mentioned:
   1- CPU socket, e.g., uncore PMU
   2- chipset
   3- GPU

I can see 1/ being indirectly achievable by specifying a CPU.
But the others are uncorrelated to either a CPU or thread.
I have already seen requests for accessing chipsets, and
seems GPU are around the corner now.

Why do you think those would be invalid targets given
the goal of this API?