linux-kernel - Re: [PATCH 2/2] perf callchain: Use global caching provided by libunwind

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Message-ID: <87bnq3j5g0.fsf@sejong.aot.lge.com>
Date:	Fri, 26 Sep 2014 14:50:39 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Jean Pihet <jean.pihet@...aro.org>
Cc:	Arun Sharma <asharma@...com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...nel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Namhyung Kim <namhyung.kim@....com>,
	LKML <linux-kernel@...r.kernel.org>, Jiri Olsa <jolsa@...hat.com>
Subject: Re: [PATCH 2/2] perf callchain: Use global caching provided by libunwind

Hi Jean,

On Wed, 24 Sep 2014 15:45:57 +0200, Jean Pihet wrote:
> Hi!
>
> Here are the test results on ARMv7 for the 2 patches. The speedup is
> about x2.1 for identical unwinding output data.
>
> 'perf record --call-graph dwarf -- stress --cpu 2 --io 2 --vm 2
> --timeout 10s' generates a 365 MB perf.data file.
>
> time perf.orig report --sort symbol --call-graph --stdio 2&>1 > /dev/null
> average on 3 runs
> real    36.736
> user   14.79
> sys    21.91
>
> time perf.libunwind.speedup report --sort symbol --call-graph --stdio
> 2&>1 > /dev/null
> average on 3 runs
> real    17.41        x2.11
> user     6.42        x2.3
> sys    10.97        x2
>
> So the patches definitely speedup the unwinding.
> FWIW: Acked-by: Jean Pihet <jean.pihet@...aro.org>

Thanks for your test!

Btw, have you checked the difference of the output before and after the
caching?

>
> For info unwinding using libdw is about 5x faster:
> time perf.libdw.speedup report --sort symbol --call-graph --stdio 2&>1
>> /dev/null
> real    0m3.484s
> user    0m2.360s
> sys    0m1.070s

Wow, it's pretty nice.  I'll take a look at the libdw unwinding later.

Thanks,
Namhyung
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