Messages in this thread |  | | | Date | Tue, 31 Mar 2009 20:12:45 +1100 | | From | Paul Mackerras <> | | Subject | Re: [PATCH 13/15] perf_counter: provide generic callchain bits |
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Corey Ashford writes:
> If this is the case, what is the exact meaning of PERF_COUNTER_SIMPLE > now? and PERF_COUNTER_GROUP? One simplification would be that reading > the fd of a group leader would always read up all of the counters in the > group (along with their enabled and running times if those bits are > set), and that reading a single counter's fd would yield only that > counter's values and times (if enabled). In effect, these two values, > PERF_COUNTER_GROUP and PERF_COUNTER_SIMPLE would no longer be necessary > at all. Other bits would be used to determine what's in the mmap'd samples.
Now that events are only read through mmap, it's quite simple - hw_event.read_format controls what read() gives you, and hw_event.record_type controls what gets put into the pages that you get with mmap.
Currently read_format and record_type don't use the same set of bit definitions. Maybe they should? I don't have a strong feeling about it, but that might be a nice simplification.
Paul.
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