perf report: Don't bother locking when adding hist entries
authorNamhyung Kim <namhyung.kim@lge.com>
Tue, 14 May 2013 02:09:03 +0000 (11:09 +0900)
committerArnaldo Carvalho de Melo <acme@redhat.com>
Tue, 28 May 2013 13:24:00 +0000 (16:24 +0300)
commitf3dd19817e5bbcae81e96571a3d42aa30a1581fb
tree46ef8e5ffa7347f397961c96751e8c391c50eab7
parent27a0dcb7adb52473dd98d285a46b764b9219d303
perf report: Don't bother locking when adding hist entries

The 'perf report'command is single-threaded, so no need to grab a lock.

Although the fast path of pthread_mutex_[un]lock() is very fast, there's
a ~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@kernel.org>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1368497347-9628-6-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
tools/perf/builtin-report.c