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...).
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