linux-kernel - Re: [RFC PATCH -tip 2/2 v2] add a scripts for pagecache usage per process

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Date:	Tue, 23 Feb 2010 19:13:22 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Tom Zanussi <tzanussi@...il.com>, Ingo Molnar <mingo@...e.hu>,
	Paul Mackerras <paulus@...ba.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Keiichi KII <k-keiichi@...jp.nec.com>,
	linux-kernel@...r.kernel.org, lwoodman@...hat.com,
	linux-mm@...ck.org, riel@...hat.com, rostedt@...dmis.org,
	akpm@...ux-foundation.org, Munehiro Ikeda <m-ikeda@...jp.nec.com>,
	Atsushi Tsuji <a-tsuji@...jp.nec.com>
Subject: Re: [RFC PATCH -tip 2/2 v2] add a scripts for pagecache usage per
 process

On Tue, 2010-02-23 at 18:54 +0100, Frederic Weisbecker wrote:

> > [PATCH] perf record: filter out perf process tracepoint events
> > 
> > The perf process itself can generate a lot of trace data, which most
> > of the time isn't of any interest.  This patch adds a predicate to the
> > kernel tracepoint filter of each recorded event type which effectively
> > screens out any event generated by perf.
> > 
> > Assuming the common case would be to ignore perf, this makes it the
> > default; the old behavior can be selected by using 'perf record -P'.
> 
> 
> I think filtering out perf from the instrumentation is a very
> desirable features.
> 
> But I see two drawbacks with this patch.
> First of all, we want to keep perf as a part of the instrumentation
> as a default behaviour I think, as it is a true part of the system
> wide load. So I would rather suggest to keep it as a default and
> have an exclude_perf option instead of include_perf.

Agreed, excluding by default doesn't seem to be a sane idea.

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