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(-)
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