On 07/03/2017 08:20 PM, Ming Lei wrote:

quoted

Right. So the two modes I'm running in are:

1. 80 null_blk devices, each with one submit_queue, with one fio job per null_blk device,
   so 80 threads total. 80 logical CPUs
2. 1 null_blk device, with 80 submit_queues, 80 fio jobs, 80 logical CPUs.

In theory, the two should result in similar numbers.

Here are the commands and fio configurations:

Scenario #1
modprobe null_blk submit_queues=80 nr_devices=1 irqmode=0

FIO config:
[global]
buffered=0
invalidate=1
bs=4k
iodepth=64
numjobs=80
group_reporting=1
rw=randrw
rwmixread=100
rwmixwrite=0
ioengine=libaio
runtime=60
time_based

[job1]
filename=/dev/nullb0

IMO it should be more reasonable to use single null_blk with 80 queues
via setting submit_queues as 80 than simply 80 null_blks.  So suggest to switch
to test 80 queues in your future test.

That should be what my Scenario #1 covers. 

Thanks,

Brian

-- 
Brian King
Power Linux I/O
IBM Linux Technology Center