On Wed, Jun 25, 2014 at 11:05:56PM -0600, Jens Axboe wrote:

On 2014-06-25 20:08, Ming Lei wrote:

quoted

Hi,

These patches try to support multi virtual queues(multi-vq) in one
virtio-blk device, and maps each virtual queue(vq) to blk-mq's
hardware queue.

With this approach, both scalability and performance on virtio-blk
device can get improved.

For verifying the improvement, I implements virtio-blk multi-vq over
qemu's dataplane feature, and both handling host notification
from each vq and processing host I/O are still kept in the per-device
iothread context, the change is based on qemu v2.0.0 release, and
can be accessed from below tree:

git://kernel.ubuntu.com/ming/qemu.git #v2.0.0-virtblk-mq.1

For enabling the multi-vq feature, 'num_queues=N' need to be added into
'-device virtio-blk-pci ...' of qemu command line, and suggest to pass
'vectors=N+1' to keep one MSI irq vector per each vq, and the feature
depends on x-data-plane.

Fio(libaio, randread, iodepth=64, bs=4K, jobs=N) is run inside VM to
verify the improvement.

I just create a small quadcore VM and run fio inside the VM, and
num_queues of the virtio-blk device is set as 2, but looks the
improvement is still obvious.

1), about scalability
- without mutli-vq feature
-- jobs=2, thoughput: 145K iops
-- jobs=4, thoughput: 100K iops
- with mutli-vq feature
-- jobs=2, thoughput: 193K iops
-- jobs=4, thoughput: 202K iops

2), about thoughput
- without mutli-vq feature
-- thoughput: 145K iops
- with mutli-vq feature
-- thoughput: 202K iops

Of these numbers, I think it's important to highlight that the 2 thread case
is 33% faster and the 2 -> 4 thread case scales linearly (100%) while the
pre-patch case sees negative scaling going from 2 -> 4 threads (-39%).

I haven't run your patches yet, but from looking at the code, it looks good.
It's pretty straightforward. See feel free to add my reviewed-by.

Rusty, do you want to ack this (and I'll slurp it up for 3.17)

Looks like I found some issues, so not yet pls.

or take this
yourself? Or something else?


-- 
Jens Axboe