[LSF/MM TOPIC][LSF/MM ATTEND] NAPI polling for block drivers

[Sagi Grimberg]

>> I agree with Jens that we'll need some analysis if we want the
>> discussion to be affective, and I can spend some time this if I
>> can find volunteers with high-end nvme devices (I only have access
>> to client nvme devices.
>
> I have a P3700 but somehow burned the FW. Let me see if I can bring it back to
> live.
>
> I also have converted AHCI to the irq_poll interface and will run some tests.
> I do also have some hpsa devices on which I could run tests once the driver is
> adopted.
>
> But can we come to a common testing methology not to compare apples with
> oranges? Sagi do you still have the fio job file from your last tests laying
> somewhere and if yes could you share it?

Its pretty basic:
--
[global]
group_reporting
cpus_allowed=0
cpus_allowed_policy=split
rw=randrw
bs=4k
numjobs=4
iodepth=32
runtime=60
time_based
loops=1
ioengine=libaio
direct=1
invalidate=1
randrepeat=1
norandommap
exitall

[job]
--

**Note: when I ran multiple threads on more cpus the performance
degradation phenomenon disappeared, but I tested on a VM with
qemu emulation backed by null_blk so I figured I had some other
bottleneck somewhere (that's why I asked for some more testing).

Note that I ran randrw because I was backed with null_blk, testing
with a real nvme device, you should either run randread or write, and
if you do a write, you can't run it multi-threaded (well you can, but
you'll get unpredictable performance...).