From: Zheng Liu <wenqing.lz@xxxxxxxxxx> Write samples in io_stat does not be counted with rw=randread, vice versa. Then, in sum_stat() function, it will cause 0/0 in calculating mean and S, and 'nan' is printed. So it should return immediately when src->samples is equal to 0. the error result is as follows: write: io=8328.0KB, bw=1582.7KB/s, iops=395 , runt= 5262msec clat (usec): min=58 , max=293353 , avg= -nan, stdev= -nan lat (usec): min=59 , max=293353 , avg= -nan, stdev= -nan bw (KB/s) : min= 92, max= 804, per=-nan%, avg= -nan, stdev= -nan the configuration file used: [global] direct=1 ioengine=psync bs=4k filename=/dev/sdb1 runtime=5 group_reporting loops=50 [read] rw=randread numjobs=8 [write] rw=randwrite numjobs=8 CC: Jens Axboe <jaxboe@xxxxxxxxxxxx> CC: Yu-ju Hong <yjhong@xxxxxxxxxx> Signed-off-by: Zheng Liu <wenqing.lz@xxxxxxxxxx> --- stat.c | 3 +++ 1 files changed, 3 insertions(+), 0 deletions(-) diff --git a/stat.c b/stat.c index d2cc775..3662fd9 100644 --- a/stat.c +++ b/stat.c @@ -618,6 +618,9 @@ static void sum_stat(struct io_stat *dst, struct io_stat *src, int nr) { double mean, S; + if (src->samples == 0) + return; + dst->min_val = min(dst->min_val, src->min_val); dst->max_val = max(dst->max_val, src->max_val); -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe fio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html