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. 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 :-(
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