On Mon, Feb 02, 2015 at 10:34:50AM +0200, Adrian Hunter wrote:
SNIP
> > but how about bump up the header version for this feature? ;-)
> >
> > currently it's:
> >
> > struct perf_file_header {
> > u64 magic;
> > u64 size;
> > u64 attr_size;
> > struct perf_file_section attrs;
> > struct perf_file_section data;
> > /* event_types is ignored */
> > struct perf_file_section event_types;
> > DECLARE_BITMAP(adds_features, HEADER_FEAT_BITS);
> > };
> >
> >
> > - we already store attrs as a FEATURE so we could omit that
> > - your patch stores only synthesized data into 'data' section (-1 idx)
> > this could be stored into separate file and get merged with the rest
> > - new header version would have 'features' section, so the features
> > position wouldnt depend on the 'data' end as of now and we could
> > easily store after all data is merged:
> >
> > struct perf_file_header {
> > u64 magic;
> > u64 size;
> > u64 attr_size;
> > struct perf_file_section features;
> > DECLARE_BITMAP(adds_features, HEADER_FEAT_BITS);
> > };
> >
> >
> > thoughts?
>
> How come the features are being written before the sample data anyway?
> I would have expected:
> - write the data (update the index in memory)
> - write the features (including index)
>
I think the problem is that the only way how to get features offset
right now is via perf_file_header::data.offset + perf_file_headerdata.size,
and we still use this section to carry 'sythesized' data, so it needs
to have correct size.
I guess we could workaround that by storing the 'perf_file_header::data'
as the last data section. That would require to treat it the same way as
all other data sections, but we could keep current header layout.
jirka
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