[RFC PATCH 0/2] Google extension to improve qemu-nvme performance

[Ming Lin]

Hi Rob & Mihai,

I wrote vhost-nvme patches on top of Christoph's NVMe target.
vhost-nvme still uses mmio. So the guest OS can run unmodified NVMe
driver. But the tests I have done didn't show competitive performance
compared to virtio-blk/virtio-scsi. The bottleneck is in mmio. Your nvme
vendor extension patches reduces greatly the number of MMIO writes.
So I'd like to push it upstream.

I port these 2 patches to newer kernel and qemu.
I use ram disk as backend to compare performance.

qemu-nvme: 29MB/s
qemu-nvme+google-ext: 100MB/s
virtio-blk: 174MB/s
virtio-scsi: 118MB/s

I'll show you qemu-vhost-nvme+google-ext number later.

root at guest:~# cat test.job 
[global]
bs=4k
ioengine=libaio
iodepth=64
direct=1
runtime=120
time_based
rw=randread
norandommap
group_reporting
gtod_reduce=1
numjobs=2

[job1]
filename=/dev/nvme0n1
#filename=/dev/vdb
#filename=/dev/sda
rw=read

Patches also available at:
kernel:
https://git.kernel.org/cgit/linux/kernel/git/mlin/linux.git/log/?h=nvme-google-ext
qemu:
http://www.minggr.net/cgit/cgit.cgi/qemu/log/?h=nvme-google-ext 

Thanks,
Ming