Messages in this thread | | | From | Ming Lei <> | Subject | [PATCH v2 0/2] block: virtio-blk: support multi vq per virtio-blk | Date | Thu, 26 Jun 2014 10:08:44 +0800 |
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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
So in my test, even for a quad-core VM, if the virtqueue number is increased from 1 to 2, both scalability and performance can get improved a lot.
TODO: - adjust vq's irq smp_affinity according to blk-mq hw queue's cpumask
V2: (suggestions from Michael and Dave Chinner) - allocate virtqueues' pointers dynamically - make sure the per-queue spinlock isn't kept in same cache line - make each queue's name different
V1: - remove RFC since no one objects - add '__u8 unused' for pending as suggested by Rusty - use virtio_cread_feature() directly, suggested by Rusty
Thanks, -- Ming Lei
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