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Date: Thu, 29 Sep 2011 18:58:20 -0600 From: David Ahern <dsahern@...il.com> To: Arnaldo Carvalho de Melo <acme@...stprotocols.net> CC: Jiri Olsa <jolsa@...hat.com>, a.p.zijlstra@...llo.nl, mingo@...e.hu, Stephane Eranian <eranian@...gle.com>, paulus@...ba.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] perf tools: Exit recording if events have non matching sample type On 09/29/2011 06:40 PM, Arnaldo Carvalho de Melo wrote: > Em Thu, Sep 29, 2011 at 05:33:42PM -0600, David Ahern escreveu: >> On 09/29/2011 05:06 PM, Arnaldo Carvalho de Melo wrote: >>>> >From what I can see sample_type has to be the same for all samples: >>>> https://lkml.org/lkml/2011/8/15/6 > >>> We could add a PERF_SAMPLE_ID2 that if present would be guaranteed >>> to be the last, or we can, as PeterZ prefers/suggests, to use one >>> mmap per sample id, then we know that if we're getting it on that >>> mmap, it has that sample_type. > >>> For record that means we need to dump each per-sample_id mmap onto a >>> separate file, i.e. use a directory, etc. > >> That seems like a major re-write of perf. Why not keep the existing >> restriction and have users who want different sample_types run >> multiple perf commands? > >> What's to be gained by refactoring the code to support multiple >> sample_types in a single command invocation? > > 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. With that change I have a patch that (mostly?) covers the rest of perf userspace to handle sample_type per evsel. David -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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