perf stat: Initialize statistics correctly

perf stat did initialize the stats structure used to compute
stddev etc. incorrectly. It merely zeroes it. But one member
(min) needs to be set to a non zero value. This causes min
to be not computed at all. Call init_stats() correctly.

It doesn't matter for stat currently because it doesn't use
min, but it's still better to do it correctly.

The other users of statistics are already correct.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/1395768699-16060-1-git-send-email-andi@firstfloor.org
Signed-off-by: Jiri Olsa <jolsa@redhat.com>

tools/perf/builtin-stat.c

@@ -174,13 +174,20 @@ static inline int perf_evsel__nr_cpus(struct perf_evsel *evsel)
 
 static void perf_evsel__reset_stat_priv(struct perf_evsel *evsel)
 {
-	memset(evsel->priv, 0, sizeof(struct perf_stat));
+	int i;
+	struct perf_stat *ps = evsel->priv;
+
+	for (i = 0; i < 3; i++)
+		init_stats(&ps->res_stats[i]);
 }
 
 static int perf_evsel__alloc_stat_priv(struct perf_evsel *evsel)
 {
 	evsel->priv = zalloc(sizeof(struct perf_stat));
-	return evsel->priv == NULL ? -ENOMEM : 0;
+	if (evsel == NULL)
+		return -ENOMEM;
+	perf_evsel__reset_stat_priv(evsel);
+	return 0;
 }
 
 static void perf_evsel__free_stat_priv(struct perf_evsel *evsel)