Number of samples needs to be greater 1 to have a variance.
Fixes nan% in perf-kvm-live output.
Signed-off-by: David Ahern <dsah...@gmail.com>
Cc: Arnaldo Carvalho de Melo <a...@ghostprotocols.net>
Cc: Ingo Molnar <mi...@kernel.org>
Cc: Frederic Weisbecker <fweis...@gmail.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Jiri Olsa <jo...@redhat.com>
Cc: Namhyung Kim <namhy...@kernel.org>
Cc: Xiao Guangrong <xiaoguangr...@linux.vnet.ibm.com>
Cc: Runzhen Wang <runz...@linux.vnet.ibm.com>
---
tools/perf/util/stat.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/perf/util/stat.c b/tools/perf/util/stat.c
index 2374212..7c59c28 100644
--- a/tools/perf/util/stat.c
+++ b/tools/perf/util/stat.c
@@ -37,7 +37,7 @@ double stddev_stats(struct stats *stats)
{
double variance, variance_mean;
- if (!stats->n)
+ if (stats->n < 2)
return 0.0;
variance = stats->M2 / (stats->n - 1);
--
1.7.10.1
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