[RFC PATCH] Perf: Fix an issue where perf report fails to show theproper percentage

From: Naveen N. Rao
Date: Fri Feb 03 2012 - 12:01:34 EST

This patch fixes an issue where perf report shows nan% for certain
perf.data files. The below is from a report for a do_fork probe:

-nan% sshd [kernel.kallsyms] [k] do_fork
-nan% packagekitd [kernel.kallsyms] [k] do_fork
-nan% dbus-daemon [kernel.kallsyms] [k] do_fork
-nan% bash [kernel.kallsyms] [k] do_fork

A git bisect shows commit f3bda2c as the cause. However, looking back through
the git history, I saw commit 640c03c which seems to have removed the
required initialization for perf_sample->period. The problem only started
showing after commit f3bda2c. The below patch re-introduces the
initialization and it fixes the problem for me.

With the below patch, for the same perf.data:

73.08% bash [kernel.kallsyms] [k] do_fork
8.97% 11-dhclient [kernel.kallsyms] [k] do_fork
6.41% sshd [kernel.kallsyms] [k] do_fork
3.85% 20-chrony [kernel.kallsyms] [k] do_fork
2.56% sendmail [kernel.kallsyms] [k] do_fork

This patch applies over current linux-tip commit 9949284.

Signed-off-by: Naveen N. Rao <naveen.n.rao@xxxxxxxxxxxxxxxxxx>
tools/perf/util/evsel.c | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index dcfefab..9a11f9e 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -463,6 +463,7 @@ int perf_event__parse_sample(const union perf_event *event, u64 type,
memset(data, 0, sizeof(*data));
data->cpu = data->pid = data->tid = -1;
data->stream_id = data->id = data->time = -1ULL;
+ data->period = 1;

if (event->header.type != PERF_RECORD_SAMPLE) {
if (!sample_id_all)

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