[PATCH] Fix deviation overflow
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/stat.c b/stat.c
index 6e55925..068aa92 100644
--- a/stat.c
+++ b/stat.c
@@ -271,7 +271,7 @@
static int calc_lat(struct io_stat *is, unsigned long *min, unsigned long *max,
double *mean, double *dev)
{
- double n;
+ double n, o;
if (is->samples == 0)
return 0;
@@ -281,12 +281,17 @@
n = (double) is->samples;
*mean = (double) is->val / n;
- *dev = 0;
+ *dev = 0.01;
- if (n <= 1)
+ if (n <= 1.0)
return 1;
- *dev = sqrt(((double) is->val_sq - (*mean * *mean) / n) / (n - 1));
+ o = (double) is->val_sq - ((*mean * *mean) / n);
+ if (o < 0.0)
+ *dev = -1.0;
+ else
+ *dev = sqrt(o / (n - 1.0));
+
return 1;
}