FIO creating empty latency log files

[Reed Crowe <Reed.Crowe@sandisk.com>]

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?

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