Re: test definition help needed

[Jeff Moyer <jmoyer@xxxxxxxxxx>]

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.

Cheers,
Jeff
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