Commit 02bf60aa authored May 04, 2010 by Anton Blanchard Committed by Arnaldo Carvalho de Melo May 04, 2010

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 <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Eric B Munson <ebmunson@us.ibm.com>
Acked-by: Eric B Munson <ebmunson@us.ibm.com>
LKML-Reference: <20100504111915.GB14636@kryten>
Signed-off-by: Anton Blanchard <anton@samba.org>
--
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

parent 11d232ec

tools/perf/util/event.c

+1 −0

Original line number	Original line	Diff line number	Diff line
	@@ -713,6 +713,7 @@ int event__parse_sample(event_t event, u64 type, struct sample_data data)
	array++;		array++;
	}		}

			data->id = -1ULL;
	if (type & PERF_SAMPLE_ID) {		if (type & PERF_SAMPLE_ID) {
	data->id = *array;		data->id = *array;
	array++;		array++;

tools/perf/util/header.c

+8 −0

Original line number	Original line	Diff line number	Diff line
	@@ -922,6 +922,14 @@ perf_header__find_attr(u64 id, struct perf_header *header)
	{		{
	int i;		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++) {		for (i = 0; i < header->attrs; i++) {
	struct perf_header_attr *attr = header->attr[i];		struct perf_header_attr *attr = header->attr[i];
	int j;		int j;