Re: Question: can anyone tell me what QD exactly a device is received from this test script

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On Fri, 22 Feb 2019 at 22:33, Jeff Moyer <jmoyer@xxxxxxxxxx> wrote:
>
> Sitsofe Wheeler <sitsofe@xxxxxxxxx> writes:
>
> > Hi,
> >
> > On Fri, 22 Feb 2019 at 16:19, Jing Booth <Jing.Booth@xxxxxxx> wrote:
> >>
> >> Hi all,
> >>
> >> In the test script shown below, it has [global] section and
> >> [nvme0n1] section. The test script is used to test a storage
> >> device. What queue depth does the storage device receive? Thanks
> >>
> >> fio --name=global --ba=16K --bs=16K --buffered=0 --ioengine=libaio
> >> --nice=-10 --rw=randrw --size=100% --status-interval=1 --ramp_time=2
> >> --runtime=5 --time_based --rwmixread=25 --group_reporting
> >> --numjobs=4 --iodepth=16 --norandommap
> >> --random_generator=tausworthe64 --randrepeat=0
> >> --percentile_list=99:99.9:99.99:99.999:99.9999:99.99999:99.999999:99.9999999
> >> --name=nvme0n1 --filename=/dev/nvme0n1 --iodepth=64
> >
> > Something like 4 if you count all jobs together (because numjobs is 4)
> > but you can check for yourself by looking at the submit line in the IO
> > depths output that fio produces.
> >
> > Did you see the warnings with the libaio engine in the
> > manual/documentation
> > (https://fio.readthedocs.io/en/latest/fio_doc.html#i-o-engine ) or the
> > warning in the iodepth option section
> > (https://fio.readthedocs.io/en/latest/fio_doc.html#cmdoption-arg-iodepth
> > )?
>
> He specified buffered=0.  The end result will by 64 * 4 = 256.  Of
> course, at the device things may differ due to splitting and/or merging
> of I/O in the kernel.

I stand corrected (I did a quick search for direct=1 in the line
posted and missed buffered=0), thanks Jeff!

I would still recommend looking at what fio reports back and you can
also use external tools like iostat to see what the lower level are
reporting too.

-- 
Sitsofe | http://sucs.org/~sits/



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