[PATCH 10/15] perf tools: Fix broken number of samples for perf report -n

From: Arnaldo Carvalho de Melo
Date: Thu Oct 06 2011 - 13:27:09 EST

From: Stephane Eranian <eranian@xxxxxxxxxx>

The perf report -n option was broken because it was not reporting the
correct number of samples depending on the sorting mode. By default,
samples are sorted by comm,dso,sym. That means that samples for the same
command (binary) get collapsed.

The hists__collapse_insert_entry() had a bug whereby it was aggregating
the number of events observed (periods) but not the number of samples.
Consequently, the number of samples reported could be below reality. The
percentage remained correct because based on the periods.

This patch fixes the problem by also aggregating the number of samples.
Here is an example:

$ perf report -n --stdio
12.38% 842 pong [kernel.kallsyms] [k] __lock_acquire

Here pong (a ctxsw stress test), is the only program running
and thus it is the only one responsible for the lock_acquire samples.

If we change the sorting mode:

$ perf report -n --stdio --sort=sym
12.38% 1732 [k] __lock_acquire

The actual number of samples is shown.

With the fix:

$ perf report -n --stdio
12.38% 1732 pong [kernel.kallsyms] [k] __lock_acquire

Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: 20111003093815.GA6393@quad">http://lkml.kernel.org/r/20111003093815.GA6393@quad
Signed-off-by: Stephane Eranian <eranian@xxxxxxxxxx>
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
tools/perf/util/hist.c | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/tools/perf/util/hist.c b/tools/perf/util/hist.c
index 82138a2..c83e458 100644
--- a/tools/perf/util/hist.c
+++ b/tools/perf/util/hist.c
@@ -279,6 +279,7 @@ static bool hists__collapse_insert_entry(struct hists *hists,

if (!cmp) {
iter->period += he->period;
+ iter->nr_events += he->nr_events;
if (symbol_conf.use_callchain) {
callchain_merge(&hists->callchain_cursor, iter->callchain,

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