linux-kernel - Re: [RFC/PATCHSET 00/14] perf report: Add support to accumulate hist periods (v2)

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Date:	Mon, 11 Nov 2013 13:17:10 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Namhyung Kim <namhyung@...nel.org>,
	Pekka Enberg <penberg@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Paul Mackerras <paulus@...ba.org>,
	Namhyung Kim <namhyung.kim@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Stephane Eranian <eranian@...gle.com>,
	Jiri Olsa <jolsa@...hat.com>,
	Rodrigo Campos <rodrigo@...g.com.ar>,
	Arun Sharma <asharma@...com>
Subject: Re: [RFC/PATCHSET 00/14] perf report: Add support to accumulate hist
 periods (v2)


* Peter Zijlstra <peterz@...radead.org> wrote:

> On Wed, Nov 06, 2013 at 12:47:01PM +0100, Ingo Molnar wrote:
>
> > I'm not too worried about call-graph 'legacies': it generates such 
> > huge perf.data files which is parsed so slowly at the moment that 
> > there's very little user base ... Anyone who absolutely needs 
> > call-graph profiling uses SysProf which performs well.
> 
> Uhm, say what? I use it, and I don't use sysprof since that thing is 
> totally not usable ;-)

You aren't a typical case at all! :-)

Just look back the example where Linus tried to use call-graph profiling 
to profile a mild 60-seconds workload (a kernel build) and came away 
reporting that his perf session locked up.

I think many other people ran into that performance problem. Those who are 
using it must be using it for far shorter workloads.

Anyway, that's all fixed now, and I do think that call-graph profiling is 
one of perf's killer features - I thought that from day 1 on when I 
suggested to Frederic that it would be really important to implement it 
;-)

Thanks,

	Ingo
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