Messages in this thread | | | Date | Wed, 14 Aug 2013 16:00:29 +0300 | From | Adrian Hunter <> | Subject | Re: [PATCH V11 09/15] perf: make events stream always parsable |
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On 14/08/13 15:48, 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>
Forgot to add Peter's ack which is here:
http://marc.info/?l=linux-kernel&m=137629757013526&w=2
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