On Fri, Oct 24, 2014 at 10:25:02AM +0300, Adrian Hunter wrote: > On 24/10/14 00:08, Arnaldo Carvalho de Melo wrote: > > Em Thu, Oct 23, 2014 at 01:45:09PM +0300, Adrian Hunter escreveu: > >> Add an index of the event identifiers. > >> > >> This is needed to queue Instruction > >> Trace samples according to the mmap > >> buffer from which they were recorded. > > > > This gets difficult to review, I end up having to look at all the > > patches together to figure out the use cases, to see if this here makes > > sense... > > > > Can you try to explain like to a seven year old? > > > > Sigh. > > > > 'id' is somethig super vague, what does this identifies? I want to make > > progress processing these patches, but with so short explanations like > > the above one, it gets difficult. > > This is the event id (also called the sample id) which is a unique number > allocated by the kernel to the event created by perf_event_open(). Events > can include the event id by having a sample type including PERF_SAMPLE_ID or > PERF_SAMPLE_IDENTIFIER. > > Currently the main use of the event id is to match an event back to the > evsel to which it belongs i.e. perf_evlist__id2evsel() > > The purpose of this patch is to make it possible to match an event back to > the mmap from which it was read. The reason that is useful is because the > mmap represents a time-ordered context (either for a cpu or for a thread). > Intel PT decodes trace information on that basis. In full-trace mode, that > information can be recorded when the Intel PT trace is read, but in > sample-mode the Intel PT trace data is embedded in a sample and it is in > that case that the "id index" is needed. > > So the mmaps are numbered (idx) and the cpu and tid recorded against the id > by perf_evlist__set_sid_idx() which is called by > perf_evlist__mmap_per_evsel(). > > That information is recorded on the perf.data file in the new "id index". > idx, cpu and tid are added to struct perf_sample_id (which is the node of > evlist's hash table to match ids to evsels). The information can be > retrieved using perf_evlist__id2sid(). Note however this all depends on > having a sample type including PERF_SAMPLE_ID or PERF_SAMPLE_IDENTIFIER, > otherwise ids are not recorded. > > The "id index" is a synthesized event record which will be created when > Intel PT sampling is used by calling perf_event__synthesize_id_index().
with above text in changelog: Acked-by: Jiri Olsa <jo...@kernel.org> thanks, jirka -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
