Commits
Waiman Long committed 91e95617429
perf report: Add --max-stack option to limit callchain stack scan When callgraph data was included in the perf data file, it may take a long time to scan all those data and merge them together especially if the stored callchains are long and the perf data file itself is large, like a Gbyte or so. The callchain stack is currently limited to PERF_MAX_STACK_DEPTH (127). This is a large value. Usually the callgraph data that developers are most interested in are the first few levels, the rests are usually not looked at. This patch adds a new --max-stack option to perf-report to limit the depth of callchain stack data to look at to reduce the time it takes for perf-report to finish its processing. It trades the presence of trailing stack information with faster speed. The following table shows the elapsed time of doing perf-report on a perf.data file of size 985,531,828 bytes. --max_stack Elapsed Time Output data size ----------- ------------ ---------------- not set 88.0s 124,422,651 64 87.5s 116,303,213 32 87.2s 112,023,804 16 86.6s 94,326,380 8 59.9s 33,697,248 4 40.7s 10,116,637 -g none 27.1s 2,555,810 Signed-off-by: Waiman Long <Waiman.Long@hp.com> Acked-by: David Ahern <dsahern@gmail.com> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Aswin Chandramouleeswaran <aswin@hp.com> Cc: David Ahern <dsahern@gmail.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Scott J Norton <scott.norton@hp.com> Cc: Stephane Eranian <eranian@google.com> Link: http://lkml.kernel.org/r/1382107129-2010-4-git-send-email-Waiman.Long@hp.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>