Messages in this thread | | | Date | Mon, 2 Feb 2015 10:15:54 +0100 | From | Jiri Olsa <> | Subject | Re: [PATCH 14/42] perf record: Add --index option for building index table |
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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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