From 02bf60aad7d5912dfcdbe0154f1bd67ea7a8301e Mon Sep 17 00:00:00 2001 From: Anton Blanchard Date: Tue, 4 May 2010 21:19:15 +1000 Subject: [PATCH] perf: Fix performance issue with perf report 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. Cc: Peter Zijlstra Cc: Paul Mackerras Cc: Ingo Molnar Cc: Frederic Weisbecker Cc: Eric B Munson Acked-by: Eric B Munson LKML-Reference: <20100504111915.GB14636@kryten> Signed-off-by: Anton Blanchard -- Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/event.c | 1 + tools/perf/util/header.c | 8 ++++++++ 2 files changed, 9 insertions(+) diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c index 1757b0ffeaa9..2477270c1d3f 100644 --- a/tools/perf/util/event.c +++ b/tools/perf/util/event.c @@ -713,6 +713,7 @@ int event__parse_sample(event_t *event, u64 type, struct sample_data *data) array++; } + data->id = -1ULL; if (type & PERF_SAMPLE_ID) { data->id = *array; array++; diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c index 2b9f898efea6..8847bec64c54 100644 --- a/tools/perf/util/header.c +++ b/tools/perf/util/header.c @@ -922,6 +922,14 @@ perf_header__find_attr(u64 id, struct perf_header *header) { 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; -- GitLab