(Adding peterz in case he has a time to answer) On Thu, 6 Sep 2012 11:19:21 -0400, Vince Weaver wrote: > On Tue, 4 Sep 2012, Namhyung Kim wrote: >> >> AFAIK the "inherit" field determines whether the event is inherited to a >> child process/thread. The "inherit_stat" is only meaningful when the >> "inherit" field is also set and it'll preserve (saved) event counts >> between context switch of the inherited processes/threads. > > Thank you for taking the time to answer! > > I'm still trying to construct a test case that shows the difference but > I'm failing.
Please note that my understanding of perf core code is not firm enough so there might be some mistakes. ;-) > > Aren't the stats *always* saved on context switch? If both of them are cloned from the same parent event context and there's no event added in the meantime. Please see perf_event_context_sched_out() calling perf_event_sync_stat. > > Does this affect what happens when you read the perf_event fd in the > inherited threads, or only from the master thread? It might. But I guess the master thread doesn't get affected from that. > > What is the expected behavior if you set inherit_thread but do not set > inherit? You meant inherit_stat, right? If so, it looks it'd be a nop since there's no inherited events. Maybe the perf tools can be changed to warn about that. Thanks, Namhyung -- To unsubscribe from this list: send the line "unsubscribe linux-perf-users" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html