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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