Re: [RFC PATCH 0/2] block: virtio-blk: support multi vq per virtio-blk

[Jens Axboe]

On 06/13/2014 11:29 AM, Ming Lei wrote:
> Hi,
> 
> This 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 problems on
> virtio-blk device 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 changes are 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-dataplane-mq
> 
> 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
> - without mutli-vq feature
> 	-- jobs=2, thoughput: 186K iops
> 	-- jobs=4, thoughput: 199K iops

Awesome! I was hoping someone would do that, and make virtio-blk take
full advantage of blk-mq.

-- 
Jens Axboe

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