linux-kernel - Re: [RFC] perf_events: support for uncore a.k.a. nest units

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Message-ID: <OF10DAFDB7.4623FE5C-ON862576F7.00569322-862576F7.0056F0E4@us.ibm.com>
Date:	Wed, 31 Mar 2010 10:49:07 -0500
From:	Maynard Johnson <mpjohn@...ibm.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Andi Kleen <andi@...stfloor.org>, cel@...ux.vnet.ibm.com,
	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	Stephane Eranian <eranian@...glemail.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Ingo Molnar <mingo@...e.hu>, Lin Ming <ming.m.lin@...el.com>,
	Philip Mucci <mucci@...s.utk.edu>,
	Paul Mackerras <paulus@...ba.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Dan Terpstra <terpstra@...s.utk.edu>,
	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
Subject: Re: [RFC] perf_events: support for uncore a.k.a. nest units

Peter Zijlstra <peterz@...radead.org> wrote on 03/31/2010 09:01:56 AM:

> [image removed]
>
> Re: [RFC] perf_events: support for uncore a.k.a. nest units
>
> Peter Zijlstra
>
> to:
>
> Corey Ashford
>
> 03/31/2010 09:02 AM
>
> Cc:
>
> Lin Ming, Ingo Molnar, LKML, Andi Kleen, Paul Mackerras, Stephane
> Eranian, Frederic Weisbecker, Xiao Guangrong, Dan Terpstra, Philip
> Mucci, Maynard Johnson, cel, Steven Rostedt, Arnaldo Carvalho de
> Melo, Masami Hiramatsu
>
> On Tue, 2010-03-30 at 15:12 -0700, Corey Ashford wrote:
> >
> > > Initially I'd not allow per-pmu-per-task contexts
> > > because then things like perf_event_task_sched_out() would get rather
> > > complex.
> >
> > Definitely.  I don't think it makes sense to have per-task context on
> > nest/uncore PMUs.  At least we haven't found any justification for it.
>
> For uncore no, but there is also the hw-breakpoint stuff that is being
> presented as a pmu, for those it would make sense to have a separate
> per-task context.
hw-breakpoint presented as a pmu?  hmmmm.  IMHO, this is an example where
shoehorning something into the perf_events subsystem that logically doesn't
belong there just makes for more complexity in the code.
>
> But doing multiple per-task contexts is something for a next step
> indeed.
>
[snip]

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