[PATCH 3/3] perf: Fix performance issue with perf report
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From: Arnaldo Carvalho de Melo on 4 May 2010 10:10 From: Anton Blanchard <anton(a)samba.org> 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 <a.p.zijlstra(a)chello.nl> Cc: Paul Mackerras <paulus(a)samba.org> Cc: Ingo Molnar <mingo(a)elte.hu> Cc: Frederic Weisbecker <fweisbec(a)gmail.com> Cc: Eric B Munson <ebmunson(a)us.ibm.com> Acked-by: Eric B Munson <ebmunson(a)us.ibm.com> LKML-Reference: <20100504111915.GB14636(a)kryten> Signed-off-by: Anton Blanchard <anton(a)samba.org> -- Signed-off-by: Arnaldo Carvalho de Melo <acme(a)redhat.com> --- tools/perf/util/event.c | 1 + tools/perf/util/header.c | 8 ++++++++ 2 files changed, 9 insertions(+), 0 deletions(-) diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c index 1757b0f..2477270 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 2b9f898..8847bec 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; -- 1.6.2.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |