* use of rwmixread option
@ 2013-01-31 23:43 Carl Zwanzig
2013-02-01 0:00 ` Jens Axboe
0 siblings, 1 reply; 2+ messages in thread
From: Carl Zwanzig @ 2013-01-31 23:43 UTC (permalink / raw)
To: fio@vger.kernel.org
Hi,
Am I correct that rwmixread/rwmixwrite are completely ignored unless readwrite=rw or =randrw? Experiments suggest yes but I can't find where this is handled in the code. (The HowTo file is silent on this.)
*Is there a description somewhere on how options are processed? Tracking the option definition in options.c to its use has eluded me.
thanks,
z!
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: use of rwmixread option
2013-01-31 23:43 use of rwmixread option Carl Zwanzig
@ 2013-02-01 0:00 ` Jens Axboe
0 siblings, 0 replies; 2+ messages in thread
From: Jens Axboe @ 2013-02-01 0:00 UTC (permalink / raw)
To: Carl Zwanzig; +Cc: fio@vger.kernel.org
On Thu, Jan 31 2013, Carl Zwanzig wrote:
> Hi,
>
> Am I correct that rwmixread/rwmixwrite are completely ignored unless
> readwrite=rw or =randrw? Experiments suggest yes but I can't find
> where this is handled in the code. (The HowTo file is silent on this.)
That is correct, see io_u.c:get_rw_ddir(). The mix is only used if the
data direciton is read-write. For pure read, always reads, for pure
writes, always writes.
> *Is there a description somewhere on how options are processed?
> Tracking the option definition in options.c to its use has eluded me.
So the options.c bits only ensure that the options are set. That is
td->o.rwmix[]. The options ensure that mixread + mixwrite == 100%. The
actual handling is in the function mentioned above, plus it interacts
with an IO issue counter. Essentially the mix is IOPS based, with
randomness for direction chosen.
--
Jens Axboe
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