On Sun, Mar 16, 2014 at 5:12 AM, Ming Lei <tom.leiming@xxxxxxxxx> wrote: > On Sat, Mar 15, 2014 at 7:10 PM, jvogt <jvogt@xxxxxxx> wrote: >> Hi list >> >> I was wondering: >> When i start >> fio --name=/srv/mail/test --size=10M --direct=1 --runtime=60 --time_based >> --group_reporting --refill_buffer --rw=read --numjobs=1 >> >> I get as result: >> read : io=1177.4MB, bw=20093KB/s, iops=5023, runt= 60000msec > > From fio/HOWTO: > > time_based If set, fio will run for the duration of the runtime > specified even if the file(s) are completely read or > written. It will simply loop over the same workload > as many times as the runtime allows. > > The same 10M file will be read many times(118), so most > of times it is read from page cache instead of the file, and > the result can't be accurate enough. > > > > Thanks, > -- > Ming Lei > -- > 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 Tested on my system and saw no difference in performance. Direct io will bypass the page cache so the only thing that comes to mind would be an on-device cache, though, I would think the difference in performance would be more dramatic if that were the case. -- 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
