* Understanding bandwidth results
@ 2013-06-30 20:46 Andrew Davidoff
2013-07-01 9:59 ` Jens Axboe
0 siblings, 1 reply; 2+ messages in thread
From: Andrew Davidoff @ 2013-06-30 20:46 UTC (permalink / raw)
To: fio
Hi,
In fio output, I see two values for bandwidth that I'd expect to be
the same, but that are different. For example, in the results from a
sync randread fileio test:
read : io=182811KB, bw=18279KB/s, iops=18279, runt= 10001msec
...
bw (KB /s): min= 966, max=21410, per=99.59%, avg=18204.94, stdev=5773.57
I realize they are close, but why are the values for bw= and avg= not
the same? I want to make sure I understand if these are not actually
reporting on the same statistic.
Also, why is per= not 100%, if this job was run with only a single
thread in a single group?
Thanks.
Andy
^ permalink raw reply [flat|nested] 2+ messages in thread* Re: Understanding bandwidth results
2013-06-30 20:46 Understanding bandwidth results Andrew Davidoff
@ 2013-07-01 9:59 ` Jens Axboe
0 siblings, 0 replies; 2+ messages in thread
From: Jens Axboe @ 2013-07-01 9:59 UTC (permalink / raw)
To: Andrew Davidoff; +Cc: fio
On Sun, Jun 30 2013, Andrew Davidoff wrote:
> Hi,
>
> In fio output, I see two values for bandwidth that I'd expect to be
> the same, but that are different. For example, in the results from a
> sync randread fileio test:
>
> read : io=182811KB, bw=18279KB/s, iops=18279, runt= 10001msec
> ...
> bw (KB /s): min= 966, max=21410, per=99.59%, avg=18204.94, stdev=5773.57
>
>
> I realize they are close, but why are the values for bw= and avg= not
> the same? I want to make sure I understand if these are not actually
> reporting on the same statistic.
>
> Also, why is per= not 100%, if this job was run with only a single
> thread in a single group?
That's just rounding and imprecise math. Should be fixed up though. It's
calculated in stat.c:show_ddir_status() and I'll be happy to take
patches :-)
--
Jens Axboe
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