perf header: Allow attributes to be written after data
With a file, to write data an offset needs to be known. Typically data follows the event attributes in a file. However, if processing a pipe the number of event attributes may not be known. It is convenient in that case to write the attributes after the data. Expand perf_session__do_write_header() to allow this when the data offset and size are known. This approach may be useful for more than just taking a pipe file to write into a data file, `perf inject --itrace` will reserve and additional 8kb for attributes, which would be unnecessary if the attributes were written after the data. Signed-off-by:Ian Rogers <irogers@google.com> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: James Clark <james.clark@linaro.org> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Kan Liang <kan.liang@linux.intel.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Nick Terrell <terrelln@fb.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Yanteng Si <siyanteng@loongson.cn> Cc: Yicong Yang <yangyicong@hisilicon.com> Link: https://lore.kernel.org/r/20240829150154.37929-6-irogers@google.comSigned-off-by:
Arnaldo Carvalho de Melo <acme@redhat.com>
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