On Mon, Sep 08, 2014 at 12:11:19PM +0200, Peter Zijlstra wrote: > On Mon, Sep 08, 2014 at 12:00:19PM +0200, Jiri Olsa wrote: > > > > no.. so the value of the counter is the sum of all the inherited events. > > > It doesn't matter if you flip it or not the sum is not affected. > > > > > > PERF_SAMPLE_READ should return the value. > > > > so I want to be able to do the leader sampling over child processes > > that means: > > - have event group with sampling leader, and the rest > > of the group events' periods being read on leader's sample > > via PERF_SAMPLE_READ sample_type > > - for each child process created I want it to do the > > same thing as the parent - sample on leader, read > > values of other events in group via PERF_SAMPLE_READ > > The thing is, PERF_SAMPLE_READ should return the exact same thing as an > actual read(), and for read() the value reported is the sum of all > events.
maybe we could make this configurable? like via new per_event_attr::option bit, keeping by default the behaviour you said > > I _think_ I know what you want, and I think I see why you'd want that, > but I'm not sure how to best do that.. Hmm.. maybe look at > 'perf_event_attr::inherit_stat' that appears to be similar. > > At which point read() vs inherit_stat might be 'broken'. Hard to know if > anybody uses that :-( I'll check, thanks jirka -- 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/
