Messages in this thread | | | Date | Mon, 12 Aug 2013 10:52:27 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH V9 09/14] perf: make events stream always parsable |
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On Mon, Aug 05, 2013 at 07:26:29PM +0300, Adrian Hunter wrote: > The event stream is not always parsable because the format of a sample > is dependent on the sample_type of the selected event. When there > is more than one selected event and the sample_types are not the > same then parsing becomes problematic. A sample can be matched to its > selected event using the ID that is allocated when the event is opened. > Unfortunately, to get the ID from the sample means first parsing it. > > This patch adds a new sample format bit PERF_SAMPLE_IDENTIFER that puts > the ID at a fixed position so that the ID can be retrieved without > parsing the sample. For sample events, that is the first position > immediately after the header. For non-sample events, that is the last > position. > > In this respect parsing samples requires that the sample_type and ID > values are recorded. For example, perf tools records struct perf_event_attr > and the IDs within the perf.data file. Those must be read first > before it is possible to parse samples found later in the perf.data file. > > Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
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