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

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Date:	Wed, 24 Sep 2014 10:04:43 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	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>,
	Jean Pihet <jean.pihet@...aro.org>,
	Arun Sharma <asharma@...com>
Subject: Re: [PATCH 2/2] perf callchain: Use global caching provided by libunwind

On Tue, 23 Sep 2014 21:53:43 +0900, Namhyung Kim wrote:
> On Tue, Sep 23, 2014 at 9:28 PM, Jiri Olsa <jolsa@...hat.com> wrote:
>> On Tue, Sep 23, 2014 at 03:30:28PM +0900, Namhyung Kim wrote:
>>> The libunwind provides two caching policy which are global and
>>> per-thread.  As perf unwinds callchains in a single thread, it'd
>>> sufficient to use global caching.
>>>
>>> This speeds up my perf report from 14s to 7s on a ~260MB data file.
>>> Although the output contains a slight difference (~0.01% in terms of
>>> number of lines printed) on callchains which were not resolved.
>>
>> hum, the speedup is nice, but what was the diff output.. any example?
>> The new version does not print some lines or different ones?
>
> I don't have the result now - will post the diff when I go to the
> office tomorrow.  But IIRC new version only adds new lines..

Okay, this is the result..  But it doesn't always make a difference.  I
can see it produces exactly same output for other (even bigger) data files.


  $ diff -U0 callchain-result.{old,new}
  --- callchain-result.old	2014-09-23 14:52:29.630711402 +0900
  +++ callchain-result.new	2014-09-23 14:52:52.709505500 +0900
  @@ -5322,0 +5323,9 @@
  +                          |          |          |          
  +                          |          |           --0.00%-- 0x406520
  +                          |          |                     0x4064f0
  +                          |          |                     |          
  +                          |          |                     |--0.00%-- 0x1ad52a0
  +                          |          |                     |          
  +                          |          |                     |--0.00%-- 0x1a0f2e0
  +                          |          |                     |          
  +                          |          |                      --0.00%-- 0x1a9e0c0
  @@ -108899,0 +108909,3 @@
  +                            |          |          0x406520
  +                            |          |          0x4064f0
  +                            |          |          0x1a9e0c0
  @@ -180410,0 +180423,9 @@
  +                          |          |          
  +                          |           --0.00%-- 0x406520
  +                          |                     0x4064f0
  +                          |                     |          
  +                          |                     |--0.00%-- 0x1ad52a0
  +                          |                     |          
  +                          |                     |--0.00%-- 0x1a0f2e0
  +                          |                     |          
  +                          |                      --0.00%-- 0x1a9e0c0
  
  $ wc -l callchain-result.{old,new}
    191412 callchain-result.old
    191433 callchain-result.new
    382845 total


Thanks,
Namhyung
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