Em Thu, May 07, 2015 at 04:39:39PM +0200, Peter Zijlstra escreveu:
> On Thu, May 07, 2015 at 11:15:20AM -0300, Arnaldo Carvalho de Melo wrote:
> > Em Thu, May 07, 2015 at 01:54:46PM +0200, Peter Zijlstra escreveu:
> > > On Thu, May 07, 2015 at 01:35:24PM +0200, Peter Zijlstra wrote:
> > > >
> > > > - dropped the @id field from the record, it is already included in the
> > > > @sample_id values.
> > >
> > > Hmm, this would force people to use sample_id; which in general is a
> > > good idea, but should we really force that on people?
> >
> > Well, if there are more than one sample, we need it, right? If there is
> > just one, we don't need it, what is different? Am I needing (even more)
> > coffee?
> >
> > /me goes read some code...
>
> So the question was, do we do:
>
> /*
> * struct {
> * struct perf_event_header header;
> * u64 id;
> * u64 lost;
> * struct sample_id sample_id;
> * };
> */
> PERF_RECORD_LOST_SAMPLES
>
> And have the id thing twice if attr.sample_id && PERF_SAMPLE_ID, but
> allow decoding if !attr.sample_id.
>
> Or force attr.sample_id && PERF_SAMPLE_ID if there's multiple events and
> do away with the extra id field, like:
>
> /*
> * struct {
> * struct perf_event_header header;
> * u64 lost;
> * struct sample_id sample_id;
> * };
> */
> PERF_RECORD_LOST_SAMPLES
>
> Should we force the use of sample_id on people?
If we have more than one event we _need_ PERF_SAMPLE_ID, to
disambiguate, if we don't, then the lost events are just for that one,
no?
- Arnaldo
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