mjhjmtu

I'm doing something like:

sudo perf record -a -g -e context-switches -e sched:* -e cpu-clock -F 499 -p XXXX -t YYY

This will record all scheduler tracepoints, all context-switches.

• Does -F only affects events right?
  Like cpu-clock for 499Hz.

Also it was specified with -a, but -p -t was also specified.

• Would that make -a useless?

Inside perf script, context switch only shows stack trace, while sched_switch shows both stack trace and switch information (next task to use the cpu).

• How are context-switch and sched events related to?

What I have noticed is that after sched_switch, there's always a context-switch, Now I'm assuming that context-switch is the sched_switch.

In this scheduling sample:

command 7447/7447 [001] 62202.663269: 329 sched:sched_waking: comm=schedmon pid=498 prio=120 target_cpu=001
command 7447/7447 [001] 62202.663274: 335 sched:sched_wakeup: schedmon:498 [120] success=1 CPU:001
command 7447/7447 [001] 62202.702887: 43294327 sched:sched_stat_runtime: comm=command pid=7447 runtime=988313 [ns] vruntime=194195593780 [ns]
command 7447/7447 [003] 62203.127899: 1 sched:sched_migrate_task: comm=rcu_sched pid=8 prio=120 orig_cpu=1 dest_cpu=3
command 7447/7447 [001] 62203.265789: 21 sched:sched_switch: command:7447 [120] R ==> kworker/u8:2:5539 [120]

• What is the unit of 62202.663269?


• What is period (number after 62202.663269)?


• In sched_waking event is comm= is the waker?


• In sched_switch event what is [120]? what is R?


• I noticed that there are sched:sched_stat_runtime and then sched:sched_waking for same thread. Why is this? Am I missing a sched sleep here?


• What to look for thread sleep?


• What to look for thread blocker? For example in condition variable wait or io, or swap, etc.


• How is the sched:sched_stat_runtime being reported? from what it seems,it it reported when thread has consumed certain vruntime.

I'm doing this because there a significant time increase of a program running under KVM.

Thanks!