Re: [Qemu-devel] [PATCH V4 00/22] Multiqueue virtio-net

[Michael S. Tsirkin]

On Wed, Jan 30, 2013 at 07:12:19PM +0800, Jason Wang wrote:
> Hello all:
> 
> This seires is an update of last version of multiqueue virtio-net support.
> 
> This series tries to brings multiqueue support to virtio-net through a
> multiqueue support tap backend and multiple vhost threads.
> 
> Patch 1 converts bitfield in TAPState to bool. Patch 2 replace assert(0) with
> abort() in tap.
> 
> To support this, multiqueue nic support were added to qemu. This is done by
> introducing an array of NetClientStates in NICState, and make each pair of 
> peers
> to be an queue of the nic. This is done in patch 3-9.
> 
> Tap were also converted to be able to create a multiple queue
> backend. Currently, only linux support this by issuing TUNSETIFF N times with
> the same device name to create N queues. Each fd returned by TUNSETIFF were a
> queue supported by kernel. Three new command lines were introduced, "queues"
> were used to tell how many queues will be created by qemu; "fds" were used to
> pass multiple pre-created tap file descriptors to qemu; "vhostfds" were used 
> to
> pass multiple pre-created vhost descriptors to qemu. This is done in patch 
> 10-15.
> 
> A method of deleting a queue and queue_index were also introduce for virtio,
> this is done in patch 16-17.
> 
> Vhost were also changed to support multiqueue by introducing a start vq index
> which tracks the first virtqueue that will be used by vhost instead of the
> assumption that the vhost always use virtqueue from index 0. This is done in
> patch 18.
> 
> The last part is the multiqueue userspace changes, this is done in patch 
> 19-22.
> 
> With this changes, user could start a multiqueue virtio-net device through
> 
> ./qemu -netdev tap,id=hn0,queues=2,vhost=on -device virtio-net-pci,netdev=hn0
> 
> Management tools such as libvirt can pass multiple pre-created fds/vhostfds 
> through
> 
> ./qemu -netdev tap,id=hn0,fds=X:Y,vhostfds=M:N -device 
> virtio-net-pci,netdev=hn0
> 
> For the one who wants to try, a git tree is available at:
> git://github.com/jasowang/qemu.git
> 
> Changes from V3:
> - convert bitfield to bool in TAPState (Blue)
> - use abort() instead of assert(0) in tap code (Blue)
> - rebase to the latest
> - fix a bug that breaks the non-tap network

This conflicts with the pull request I sent, in partucular this adds a
layout assumption.  In the hope this will accelerate things, I did a
rebase and a trivial test with single queue only and it seems ok:

git://github.com/mstsirkin/qemu.git pci

There were some warnings about whitespace at EOF but
otherwise seems ok.

-- 
MST