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

[Michael S. Tsirkin]

On Thu, Jan 31, 2013 at 04:21:49PM +0200, Michael S. Tsirkin wrote:
> 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.

Pushed to my pci branch on kernel.org too.

> -- 
> MST