Re: FIO creating empty latency log files

[Jens Axboe <axboe@kernel.dk>]

On 10/28/2015 12:41 AM, Buttetsu Batou wrote:
> On 06/04/2015 05:09 PM, Reed Crowe wrote:
>> Using this version of FIO:
>> * io-threads
>>      master
>> rcrowe@rcrowe-desktop:~/fio_iothreads/fio$ ./fio --version
>> fio-2.2.7-14-g00b2
>>
>> I have a job file which looks like this:
>>
>> [global]
>> ioengine=libaio
>> direct=1
>> numjobs=1
>> bs=4k
>> iodepth=300
>> rw=randwrite
>> randrepeat=0
>> io_submit_mode=offload
>> rate_iops=8070
>> time_based=1
>> runtime=1m
>>
>> [slow_write]
>> filename=/mnt/test1/testfile.io
>> write_lat_log=/tmp/fio_lat
>>
>> And it produces empty files:
>> -rw-r--r-- 1 root   root         0 Jun  4 14:34 fio_lat_clat.1.log
>> -rw-r--r-- 1 root   root         0 Jun  4 14:34 fio_lat_lat.1.log
>> -rw-r--r-- 1 root   root         0 Jun  4 14:34 fio_lat_slat.1.log
>>
>> What am I missing?
>
> I am seeing this behavior in the latest release fio-2.2.10 and in
> master fio-2.2.10-29-g8a68 but I am not using offload.
>
> Is anyone currently able to successfully generate log output? If so
> could you share your fio version and your config?
>
> Here is the job file I am using at the moment.. have tried variations
> on these settings and different fio versions back to 2.0.15 but always
> the same empty output:
>
> [write]
> group_reporting=1
> numjobs=8
> ioengine=posixaio
> io_submit_mode=inline
> stonewall
> rw=write
> bs=32k
> time_based=1
> runtime=10
> filesize=64k
> directory=/tmp
> per_job_logs=1
> write_bw_log=write_bw
> write_iops_log=write_iops
>
> Updated the issue reported here:
>
> https://github.com/axboe/fio/issues/29
>
> Thank you for any ideas you may have!

I think your issue is because you set filesize=64k. Your job basically 
sets up 8 files of 64k each, then writes to them for 10 seconds. This 
means that the fio main loop keeps re-entering for every 64k for each 
thread. The bandwidth/iops is averaged over a window of 500msec by 
default, and the main loop runs for much shorter than that since it only 
does 64k each time. Hence you never get logged any entries.

Now, it should work. If you comment out these two lines:

memcpy(&td->bw_sample_time, &td->start, sizeof(td->start));
memcpy(&td->iops_sample_time, &td->start, sizeof(td->start));

in backend.c around 1568/1569, then I suspect the logging should improve 
for you. I'll have to see if we can safely do that without making other 
changes, before committing a change like that.t

-- 
Jens Axboe