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

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Message-ID: <CAFrcx1mqZZYbXdR80RxMP2OXf7B5xEqQymFmKr=JPh3jCz-Huw@mail.gmail.com>
Date:	Fri, 26 Sep 2014 09:14:41 +0200
From:	Jean Pihet <jean.pihet@...aro.org>
To:	Namhyung Kim <namhyung@...nel.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,

On 26 September 2014 07:50, Namhyung Kim <namhyung@...nel.org> wrote:
> 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?
Yes the output is identical (as stated here above).

>
>>
>> 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

Thanks for the patches!
Jean
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