Messages in this thread | | | Date | Thu, 29 Sep 2011 20:41:17 -0600 | From | David Ahern <> | Subject | Re: [PATCH] perf tools: Exit recording if events have non matching sample type |
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On 09/29/2011 08:21 PM, Arnaldo Carvalho de Melo wrote: > Em Thu, Sep 29, 2011 at 06:58:20PM -0600, David Ahern escreveu: >> On 09/29/2011 06:40 PM, Arnaldo Carvalho de Melo wrote: >>> This comes from time to time: >>> >>> http://us.generation-nt.com/answer/bug-perf-event-sampling-buffer-format-cannot-handle-multi-event-sampling-help-202985832.html >>> >>> The whole point of sample_type is to ask for just what is needed for >>> some specific event so that we reduce the per sample footprint. >>> >>> So we allow for multiple types of events to be on the same stream, but >>> not for them to have just what each need, its a limitation, one that we >>> can solve. I see no reason not to solve it :-) >>> >>> The evsel/evlist classes were designed to abstract away such details, >>> i.e. perf_evlist__mmap should notice different sample_types and sort >>> this out transparently. >>> >>> And then perf_evlist__mmap_read(evlist, idx), evlist->nr_mmaps should be >>> enough to process the events :-) >>> >>> - Arnaldo >> >> An ABI change fixes the root cause of the current problem -- put an id >> in perf_event_header. The id maps to the evsel which has the >> sample_type. Right now you have to parse the sample to get the id to get >> the evsel. > > This id is not always needed, so it shouldn't go to perf_event_header. > Peter, can you comment here? ;-)
I'm talking about a new 'id' that would always be needed *for samples* -- it identifies the evsel it is associated with. The evsel has the sample type. The sample_type is then used to parse it. Seems like a simpler solution then having mmap's per sample type and then writing separate files.
David
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