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SubjectRe: [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:
>>> 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:
> 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.


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