[PATCH] Fix deviation overflow

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

diff --git a/fio.h b/fio.h
index d55a1e31c292b9f40dd57f8c1d72308f72e3f665..4bb1f6c6d275a639e180ed3fcf53b2de32e1c4a5 100644 (file)
--- a/fio.h
+++ b/fio.h
@@ -25,8 +25,8 @@ enum fio_ddir {
 };
 
 struct io_stat {
-       unsigned long val;
-       unsigned long val_sq;
+       unsigned long long val;
+       unsigned long long val_sq;
        unsigned long max_val;
        unsigned long min_val;
        unsigned long samples;

diff --git a/stat.c b/stat.c
index 6e55925b1cf288ebadc565a4d4c506248ed22b9e..068aa923e7203e2996ade5a5d857d6189339d3a7 100644 (file)
--- a/stat.c
+++ b/stat.c
@@ -271,7 +271,7 @@ void update_rusage_stat(struct thread_data *td)
 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 @@ static int calc_lat(struct io_stat *is, unsigned long *min, unsigned long *max,
 
        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;
 }