Stat summation fixup

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

diff --git a/stat.c b/stat.c
index 5470c87f226d56dffa27f6a3f4c8f60c0d30dfff..07c9b62e26907bd8dbd8f8d4b72203a90a868a96 100644 (file)
--- a/stat.c
+++ b/stat.c
@@ -579,8 +579,8 @@ static void __sum_stat(struct io_stat *dst, struct io_stat *src, int nr)
                mean = src->mean;
                S = src->S;
        } else {
-               mean = ((src->mean * (double) nr) + dst->mean) / ((double) nr + 1.0);
-               S = ((src->S * (double) nr) + dst->S) / ((double) nr + 1.0);
+               mean = ((src->mean * (double) (nr - 1)) + dst->mean) / ((double) nr);
+               S = ((src->S * (double) (nr - 1)) + dst->S) / ((double) nr);
        }
 
        dst->mean = mean;