linux-kernel - Re: [RFC/PATCH 10/10] perf tools: Change default calchain percent limit to 0.005%

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Message-ID: <1453937649.11866.2.camel@kernel.org>
Date:	Thu, 28 Jan 2016 08:34:09 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Jiri Olsa <jolsa@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Wang Nan <wangnan0@...wei.com>,
	Taeung Song <treeze.taeung@...il.com>
Subject: Re: [RFC/PATCH 10/10] perf tools: Change default calchain percent
 limit to 0.005%

Hi Andi,

On Wed, 2016-01-27 at 17:06 +0100, Andi Kleen wrote:
> On Thu, Jan 28, 2016 at 12:40:57AM +0900, Namhyung Kim wrote:
> > The current default limit of 0.5% is (mostly) for 'fractal' mode
> > which
> > calculates the percentage relatively.  As we changed the default
> > callchain mode to 'graph', the existing limit is too high IMHO.
> > Normally there're many entries under 0.5% overhead, it'd be
> > supprising
> > that they don't show callchains.
> 
> It's too small imho. On more complex workloads with a lot of user
> space
> code we often end up with default perf report --stdio callgraph output
> of several
> hundred KB, and most of it is useless as it is only very small.

Do you think it's better to keep current default?  Or do you suggest
different value?

Thanks,
Namhyung