linux-kernel - Re: [PATCH] perf: Fix performance issue with perf report

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Date:	Tue, 4 May 2010 12:56:40 +0100
From:	Eric B Munson <ebmunson@...ibm.com>
To:	Anton Blanchard <anton@...ba.org>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>, Ingo Molnar <mingo@...e.hu>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf: Fix performance issue with perf report

On Tue, 04 May 2010, Anton Blanchard wrote:

> 
> On a large machine we spend a lot of time in perf_header__find_attr when
> running perf report. 
> 
> If we are parsing a file without PERF_SAMPLE_ID then for each sample we call
> perf_header__find_attr and loop through all counter IDs, never finding a match.
> As the machine gets larger there are more per cpu counters and we spend an
> awful lot of time in there.
> 
> The patch below initialises each sample id to -1ULL and checks for this in
> perf_header__find_attr. We may need to do something more intelligent eventually
> (eg a hash lookup from counter id to attr) but this at least fixes the most
> common usage of perf report.
> 
> Signed-off-by: Anton Blanchard <anton@...ba.org>

Acked-by: Eric B Munson <ebmunson@...ibm.com>

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