linux-kernel - [PATCH 3/3] perf: Fix performance issue with perf report

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Message-Id: <1272981607-28723-4-git-send-email-acme@infradead.org>
Date:	Tue,  4 May 2010 11:00:07 -0300
From:	Arnaldo Carvalho de Melo <acme@...radead.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	linux-kernel@...r.kernel.org, Anton Blanchard <anton@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>, Ingo Molnar <mingo@...e.hu>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Eric B Munson <ebmunson@...ibm.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH 3/3] perf: Fix performance issue with perf report

From: Anton Blanchard <anton@...ba.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@...llo.nl>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Eric B Munson <ebmunson@...ibm.com>
Acked-by: Eric B Munson <ebmunson@...ibm.com>
LKML-Reference: <20100504111915.GB14636@...ten>
Signed-off-by: Anton Blanchard <anton@...ba.org>
--
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.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

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