linux-kernel - [03/28] perf evsel: Fix an issue where perf report fails to show the proper percentage

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Date:	Thu, 16 Feb 2012 16:55:37 -0800
From:	Greg KH <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Robert Richter <robert.richter@....com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	"Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [03/28] perf evsel: Fix an issue where perf report fails to show the proper percentage

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>

commit a4a03fc7ef89020baca4f19174e6a43767c6d78a upstream.

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.

Problem introduced in:

$ git describe 640c03c
v2.6.37-rc3-83-g640c03c

Cc: Ananth N Mavinakayanahalli <ananth@...ibm.com>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Robert Richter <robert.richter@....com>
Cc: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20120203170113.5190.25558.stgit@localhost6.localdomain6
Signed-off-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 tools/perf/util/evsel.c |    1 +
 1 file changed, 1 insertion(+)

--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -390,6 +390,7 @@ int perf_event__parse_sample(const union

 	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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