linux-kernel - Re: [tip:perf/core] perf/ftrace: Optimize perf/tracepoint interaction for single events

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Message-ID: <20100519082335.GG5704@nowhere>
Date:	Wed, 19 May 2010 10:23:36 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	mingo@...hat.com, hpa@...or.com, paulus@...ba.org, acme@...hat.com,
	linux-kernel@...r.kernel.org, efault@....de, rostedt@...dmis.org,
	tglx@...utronix.de, mingo@...e.hu,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:perf/core] perf/ftrace: Optimize perf/tracepoint
	interaction for single events

On Wed, May 19, 2010 at 10:18:43AM +0200, Peter Zijlstra wrote:
> On Wed, 2010-05-19 at 09:58 +0200, Frederic Weisbecker wrote:
> > On Tue, May 18, 2010 at 05:15:42PM +0000, tip-bot for Peter Zijlstra wrote:
> > > Commit-ID:  4f41c013f553957765902fb01475972f0af3e8e7
> > > Gitweb:     http://git.kernel.org/tip/4f41c013f553957765902fb01475972f0af3e8e7
> > > Author:     Peter Zijlstra <a.p.zijlstra@...llo.nl>
> > > AuthorDate: Tue, 18 May 2010 18:08:32 +0200
> > > Committer:  Ingo Molnar <mingo@...e.hu>
> > > CommitDate: Tue, 18 May 2010 18:35:46 +0200
> > > 
> > > perf/ftrace: Optimize perf/tracepoint interaction for single events
> > > 
> > > When we've got but a single event per tracepoint
> > > there is no reason to try and multiplex it so don't.
> > > 
> 
> > I haven't seen this patch going.
> > 
> > But yeah that's a nice optimization for UP machines.
> 
> Uhm, doesn't have anything to do with UP machines... it works quite well
> on SMP as well.
> 
> Its about tracepoints with a single event attached.


Yeah, then if you launch perf sched for example, you'll have NR_CPU perf events
attached to each lock trace events, since we create one event per cpu.

Or may be I'm somewhat confused...

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