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>

diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
index 1757b0ffeaa97a29812b4727d451305110c9ba3f..2477270c1d3fe372dcdb6cf840356a2e3846a8fd 100644 (file)
--- 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 2b9f898efea6479290018d3aa7c6339586d4b45f..8847bec64c54119fc0e006dbd6350b231203dbd9 100644 (file)
--- 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;