Messages in this thread | | | Subject | Re: [PATCH 00/11] perf tool: Add PERF_SAMPLE_READ sample read support | From | Namhyung Kim <> | Date | Sat, 27 Oct 2012 00:39:06 +0900 |
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2012-10-26 (금), 12:23 +0200, Jiri Olsa: > On Fri, Oct 26, 2012 at 11:14:45AM +0200, Peter Zijlstra wrote: > > I haven't actually looked at the implementation, but I understood it to > > be a group modifier, not an event modifier. > > we might want to be able to use PERF_SAMPLE_READ for single event > same as for groups
What is the merits of doing it?
> > the difference between single event and group 'S' modifier: > > $ ./perf record -e 'cycles:S' ls > - records 'cycles' samples and read period value via PERF_SAMPLE_READ > > $ ./perf record -e '{cycles,cache-misses}:S' > - samples just on 'cycles' samples and read both period values > (cycles and cache-misses) via PERF_SAMPLE_READ group format > > $ ./perf record -e '{cycles,cache-misses}:S,instructions' ls > $ ./perf record -e '{cycles:S,cache-misses},instructions' ls > $ ./perf record -e 'cycles:S,instructions' ls > - non matching sample_type > > hm, thats the unique sample_type issue again ;) Once we set > PERF_SAMPLE_READ for event or group, we need to set it for > all other events in session, otherwise the report fails
Sorry, I don't understand why we need to set it for all events. Just setting it for a group is not sufficient? Please shed some light on this.
Thanks, Namhyung
> > sooo, it looks like: > - global record '-S' option instead, setting PERF_SAMPLE_READ sample type > globaly for all events > - and ':S' group modifier to enable sampling only on leader > with group format reading for the rest of the group > - ':S' group modifier alone would imply -S > > How about that? > > thanks, > jirka
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