On 2011-02-07 15:35, Jeff Moyer wrote:
> Jens Axboe <jaxboe@xxxxxxxxxxxx> writes:
>
>> On 2011-02-04 20:21, Steven Pratt wrote:
>>> I am trying to create a job file that randomly select a file form an imported list and reads the entire file sequentially. Them moves to the next file. I also want multiple jobs(processe) running the same workload. I have this:
>>>
>>> [global]
>>> bs=4k
>>> time_based=1
>>> runtime=15m
>>> iodepth=4
>>> rw=read
>>> ioengine=libaio
>>> time_based=1
>>> ramp_time=600s
>>> norandommap
>>>
>>> [job1]
>>> opendir=/${FIO_MOUNT}/session1/small_file1
>>> file_service_type=sequential
>>> numjobs=8
>>>
>>>
>>>
>>> I used file_service_type=sequential because tought without it it would
>>> only do a single read (block) from the file before switching to a
>>> different file, which is not what I want. The issue with this test as
>>> written is it seems like all the fio processes choose files in the
>>> same order so I get way more cache hits than I want. I want this to be
>>> more of a random file selection, but with reading whole file. Any
>>> advice?
>>
>> file_service_type=random:<largenum>
>>
>> should do what you need, I think. If you ensure that <largenum> is
>> sufficiently large that the file will always be finished before you run
>> out, then that should work.
>
> Also note that with ioengine=libaio, you'll also want to specify direct
> io (otherwise io_submit will block until the I/O is complete). If you
> really want buffered, then you need to choose a different io engine.
Good point. I used to have a warning for that, but dropped it since it
got annoying when I was testing the buffered aio patches. Perhaps I
should reinstate it.
In any case, if the result is inspected, it'll be apparent that the
queue depth was 1 throughout the run.
--
Jens Axboe
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