On Wed, Jul 11, 2012 at 04:33:41PM +0200, Peter Zijlstra wrote: > On Wed, 2012-07-11 at 16:31 +0200, Frederic Weisbecker wrote: > > On Wed, Jul 11, 2012 at 06:14:58PM +0400, Andrew Vagin wrote: > > > A few events are interesting not only for a current task. > > > For example, sched_stat_* are interesting for a task, which > > > wake up. For this reason, it will be good, if such events will > > > be delivered to a target task too. > > > > > > Now a target task can be set by using __perf_task(). > > > > > > The original idea and a draft patch belongs to Peter Zijlstra. > > > > > > I need this events for profiling sleep times. sched_switch is used for > > > getting callchains and sched_stat_* is used for getting time periods. > > > This events are combined in user space, then it can be analized by > > > perf tools. > > > > We've talked about that numerous times. But I still don't really > > understand why you're not using sched switch events and compute > > the difference between schedule in and schedule out. > > > > I think you said that's because you got too much events with sched > > switch. Are you loosing events? Otherwise I don't see why it's > > a problem. > > > > Also the sched_stat_sleep event produce an event which period equals the > > time slept. Internally, perf split this into as many events as that period > > because the requested period for trace events is 1 by default. We probably > > should allow to send events with a higher number than the one requested. > > This > > this produce sometimes a huge pile of events, and that even often result in > > tons of lost events. We definetly need to fix that. > > > > In the meantime you'll certainly get saner results by just recording > > sched switch events. > > Not really, there's an arbitrary large delay between wakeup and getting > scheduled back in, which is unrelated to the cause that you went to > sleep. > > The wants the time between going to sleep and getting woken up, > sched_switch simply doesn't give you that.
In this case he can just record sched wakeup as well. With sched_switch + sched_wakeup, he'll unlikely lose events. With sched_stat_sleep he will lose events, unless we fix this period demux thing. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
