perf sched: Add sched latency profiling
Add the -l --latency option that reports statistics about the
scheduler latencies.
For now, the latencies are measured in the following sequence
scope:
- task A is sleeping (D or S state)
- task B wakes up A
^
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|
latency timeframe
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v
- task A is scheduled in
Start by recording every scheduler events:
perf record -e sched:*
and then fetch the results:
perf sched -l
Tasks count total avg max
migration/0 2 39849 19924 28826
ksoftirqd/0 7 756383 108054 373014
migration/1 5 45391 9078 10452
ksoftirqd/1 2 399055 199527 359130
events/0 8 4780110 597513 4500250
events/1 9 6353057 705895 2986012
kblockd/0 42 37805097 900121 5077684
The snapshot are in nanoseconds.
- Count: number of snapshots taken for the given task
- Total: total latencies in nanosec
- Avg : average of latency between wake up and sched in
- Max : max snapshot latency
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
1 file changed