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Gmane
From: Andrew Vagin <avagin <at> openvz.org>
Subject: [PATCH 0/4] perf: Teach perf tool to profile sleep times (v2)
Newsgroups: gmane.linux.kernel
Date: Tuesday 7th August 2012 12:56:01 UTC (over 4 years ago)
This functionality helps to analize where a task sleeps or waits locks.
This feature can help to investigate a scalability problems.

The main idea is that we can combine sched_switch and sched_stat_sleep
events.
sched_switch contains a callchain, when a task starts sleeping.
sched_stat_sleep contains a time period for which a task slept.

This series teaches "perf inject" to combine this events.

All kernel related patches were committed committed in 3.6-rc1.

Here is an example of a report:
$ cat ~/foo.c
....
          for (i = 0; i <  10; i++) {
                  ts1.tv_sec = 0;
                  ts1.tv_nsec = 10000000;
                  nanosleep(&ts1, NULL);

                  tv1.tv_sec = 0;
                  tv1.tv_usec = 40000;
                  select(0, NULL, NULL, NULL,&tv1);
          }
...

$ ./perf record -e sched:sched_stat_sleep -e sched:sched_switch \
		-e sched:sched_process_exit -gP -o ~/perf.data.raw ~/foo
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.015 MB /root/perf.data.raw (~661
samples) ]
$ ./perf inject -v -s -i ~/perf.data.raw -o ~/perf.data
$ ./perf report -i ~/perf.data
# Samples: 40  of event 'sched:sched_switch'
# Event count (approx.): 1005527702
#
# Overhead  Command      Shared Object          Symbol
# ........  .......  .................  ..............
#
   100.00%      foo  [kernel.kallsyms]  [k] __schedule
                |
                --- __schedule
                    schedule
                   |          
                   |--79.81%-- schedule_hrtimeout_range_clock
                   |          schedule_hrtimeout_range
                   |          poll_schedule_timeout
                   |          do_select
                   |          core_sys_select
                   |          sys_select
                   |          system_call_fastpath
                   |          __select
                   |          __libc_start_main
                   |          
                    --20.19%-- do_nanosleep
                              hrtimer_nanosleep
                              sys_nanosleep
                              system_call_fastpath
                              __GI___libc_nanosleep
                              __libc_start_main

Andrew Vagin (3):
  perf: teach "perf inject" to work with files
  perf: teach perf inject to merge sched_stat_* and sched_switch events
  perf: mark a dso if it's used

 tools/perf/builtin-inject.c |  139
++++++++++++++++++++++++++++++++++++++++---
 tools/perf/util/build-id.c  |    2 +-
 tools/perf/util/build-id.h  |    5 ++
 3 files changed, 137 insertions(+), 9 deletions(-)
 
CD: 2ms