linux-kernel - Re: [PATCH 0/4] perf tools: New comm infrastructure

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Date:	Tue, 17 Sep 2013 14:54:22 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Jiri Olsa <jolsa@...hat.com>, David Ahern <dsahern@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Stephane Eranian <eranian@...gle.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 0/4] perf tools: New comm infrastructure

Hi Ingo,

On Sat, 14 Sep 2013 08:11:49 +0200, Ingo Molnar wrote:
> * Frederic Weisbecker <fweisbec@...il.com> wrote:
>> My patches and Namhyung's should improve the comm situation a lot but we 
>> can't do much miracle. The only way would be perhaps to be able to limit 
>> the deepness of the callchain branches.
>> 
>> Now may be we can find other big contention point in perf. It's possible 
>> we also have some endless loop somewhere.
>
> Well, it was the 100,000+ step linear list walk that was causing 90% of 
> the slowness here. Namhyung's patch should dramatically improve that. I 
> guess time for someone to post a combined tree so that it can be tested 
> all together?

I pushed combined tree to 'perf/callchain-v2' branch in my tree

  git://git.kernel.org/pub/scm/linux/kernel/git/namhyung/linux-perf.git


Please note that I also pushed other versions (v[1-3]).  The v1 is my
previous rbtree conversion patch, v2 adds Frederic's new comm
infrastructure series on top and v3 adds my revised patch to refer
current comm [1] on top of v2.

I did my own test again among them.  Test data is 400MB perf.data file
created by parallel kernel build.

  $ ls -lh perf.data.big
  -rw-------. 1 namhyung namhyung 400M Sep  9 10:21 perf.data.big

For more precise result, I changed cpufreq governor to 'performance'

  # echo performance > /sys/devices/system/cpu/cpu3/cpufreq/scaling_governor

and run perf report on the cpu.

  $ taskset -c 3 time -p perf --no-pager report --stdio -i perf.data.big > /dev/null

I ran it multiple times for each case and the results did not vary much.

        baseline	    v1            v2              v3
  ----------------------------------------------------------
  real    380.17	 12.63 	       10.02		9.03
  user    378.86	 11.95 	        9.66		8.69
  sys       0.70	  0.65 	        0.33		0.34


I also tried to cache latest result and reuse it when adding a callchain
(in callchain_append() function) but it only hits ~5% and did not help
the performance.

Thanks,
Namhyung


[1] https://lkml.org/lkml/2013/9/16/565
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