Messages in this thread | | | Date | Sun, 1 Feb 2015 19:06:35 +0100 | From | Jiri Olsa <> | Subject | Re: [PATCH 14/42] perf record: Add --index option for building index table |
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On Thu, Jan 29, 2015 at 05:06:55PM +0900, Namhyung Kim wrote: > The new --index option will create indexed data file which can be > processed by multiple threads parallelly. It saves meta event and > sample data in separate files and merges them with an index table. > > To build an index table, it needs to know exact offsets and sizes for > each sample data. However the offset only can be calculated after the > feature data is fixed, and to save feature data it needs to access to > the sample data because it needs to mark used DSOs for build-id table. > > So I ended up with reserving 1MB hole for the feature data area and then > put sample data and calculated offsets. Now an indexed perf data file > will look like below: > > +---------------------+ > | file header | > |---------------------| > | | > | meta events | > | | > |---------------------| > | feature data | > | (contains index) -+--+ > |---------------------| | > | ~1MB hole | | > |---------------------| | > | | | > | sample data[1] <-+--+ > | | | > |---------------------| | > | | | > | sample data[2] <-|--+ > | | | > |---------------------| | > | ... | ... > +---------------------+
I also dont see how to store it in a nice way under current header layout, 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? jirka
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