On Thu, 15 Apr 2021 15:09:50 +0200 Daniel Bristot de Oliveira <bristot@xxxxxxxxxx> wrote: > But for the osnoise tracer the cpus file is really useful. For instance, on a > system with the CPU 7 isolated: > > ----- %< ----- > # echo 7 > osnoise/cpus > # echo target_cpu == 7 > events/sched/sched_wakeup/filter > # echo stacktrace if target_cpu == 7 > events/sched/sched_wakeup/trigger > # echo 1 > events/sched/sched_wakeup/enable > # echo osnoise:thread_noise > set_event > # echo osnoise > current_tracer > # cat trace > [find...] > kworker/0:1-7 [000] d..5 1820.717780: <stack trace> > => trace_event_raw_event_sched_wakeup_template > => __traceiter_sched_wakeup > => ttwu_do_wakeup > => try_to_wake_up > => __queue_work > => queue_delayed_work_on > => vmstat_shepherd > => process_one_work > => worker_thread > => kthread > => ret_from_fork > kworker/7:1-410 [007] d..3 1820.717790: thread_noise: kworker/7:1:410 start 1820.717786519 duration 3626 ns > osnoise/7-1000 [007] .... 1821.582340: 1000000 90 99.99100 15 1 0 12 6 1 > ----- >% ----- > > It was possible to easily find that the '1' thread noise was a kworker, > dispatched from CPU 0, and that it was dispatched by "vmstat_shepherd". > > Also, the osnoise dir is not added to a new instance... so, it only > costs "one" file... Every file counts. ;-) What you did not articulate well, is that you want the other trace points to be traced on all CPUs (maybe) when the osnoise threads are on a few (or vice versa). OK, for osnoise, I can see how it is useful. But as you said above, for hwlat tracer, it's not as useful. -- Steve
