Messages in this thread Patch in this message | | | Date | Tue, 4 May 2010 21:19:15 +1000 | From | Anton Blanchard <> | Subject | [PATCH] perf: Fix performance issue with perf report |
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On a large machine we spend a lot of time in perf_header__find_attr when running perf report.
If we are parsing a file without PERF_SAMPLE_ID then for each sample we call perf_header__find_attr and loop through all counter IDs, never finding a match. As the machine gets larger there are more per cpu counters and we spend an awful lot of time in there.
The patch below initialises each sample id to -1ULL and checks for this in perf_header__find_attr. We may need to do something more intelligent eventually (eg a hash lookup from counter id to attr) but this at least fixes the most common usage of perf report.
Signed-off-by: Anton Blanchard <anton@samba.org> --
Index: linux.trees.git/tools/perf/util/event.c =================================================================== --- linux.trees.git.orig/tools/perf/util/event.c 2010-05-03 20:20:54.000000000 +1000 +++ linux.trees.git/tools/perf/util/event.c 2010-05-04 21:15:20.000000000 +1000 @@ -713,6 +713,7 @@ int event__parse_sample(event_t *event, array++; } + data->id = -1ULL; if (type & PERF_SAMPLE_ID) { data->id = *array; array++; Index: linux.trees.git/tools/perf/util/header.c =================================================================== --- linux.trees.git.orig/tools/perf/util/header.c 2010-05-03 20:20:54.000000000 +1000 +++ linux.trees.git/tools/perf/util/header.c 2010-05-04 21:15:20.000000000 +1000 @@ -923,6 +923,14 @@ perf_header__find_attr(u64 id, struct pe { int i; + /* + * We set id to -1 if the data file doesn't contain sample + * ids. Check for this and avoid walking through the entire + * list of ids which may be large. + */ + if (id == -1ULL) + return NULL; + for (i = 0; i < header->attrs; i++) { struct perf_header_attr *attr = header->attr[i]; int j;
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