linux-kernel - Re: [PATCH 5/9] perf report: Don't be bothered with locking when adding hist entries

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Message-ID: <20130517143944.GF3848@krava.brq.redhat.com>
Date:	Fri, 17 May 2013 16:39:44 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...nel.org>,
	Namhyung Kim <namhyung.kim@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 5/9] perf report: Don't be bothered with locking when
 adding hist entries

On Tue, May 14, 2013 at 11:09:03AM +0900, Namhyung Kim wrote:
> From: Namhyung Kim <namhyung.kim@....com>
> 
> The perf report is single-threaded, so no need to grab a lock.
> Although the fast path of pthread_mutex_[un]lock() is very fast,
> there's ~3% gain by eliminating it when we have huge sample data.
> 
>   $ perf record -a -F 100000 -o perf.data.bench -- perf bench sched all
>   $ perf record -e cycles:upp -o perf.data.before -- \
>   > perf report -i perf.data.bench --stdio > /dev/null
>   ... apply this patch ...
>   $ perf record -e cycles:upp -o perf.data.after -- \
>   > perf report -i perf.data.bench --stdio > /dev/null
>   $ perf diff perf.data.{before,after} | grep pthread
>              +0.02%  libpthread-2.15.so  [.] _pthread_cleanup_push_defer
>              +0.02%  libpthread-2.15.so  [.] _pthread_cleanup_pop_restore
>      0.05%   -0.05%  perf                [.] pthread_mutex_unlock@plt
>      0.05%   -0.05%  perf                [.] pthread_mutex_lock@plt
>      1.01%   -1.01%  libpthread-2.15.so  [.] pthread_mutex_lock
>      1.68%   -1.68%  libpthread-2.15.so  [.] __pthread_mutex_unlock_usercnt
>      0.05%   -0.05%  libpthread-2.15.so  [.] pthread_mutex_unlock
> 
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> ---
>  tools/perf/builtin-report.c | 4 ----
>  1 file changed, 4 deletions(-)

nice :)

Acked-by: Jiri Olsa <jolsa@...hat.com>

jirka
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