On Thu, Aug 16, 2012 at 03:27:57PM +0100, Chris Webb wrote: > "Michael S. Tsirkin" <m...@redhat.com> writes: > > > On Thu, Aug 16, 2012 at 10:20:05AM +0100, Chris Webb wrote: > > > > > For example, I can run > > > > > > ip addr add 192.168.1.2/24 dev eth0 > > > ip link set eth0 up > > > ip link add link eth0 name tap0 address 02:02:02:02:02:02 type macvtap > > > mode bridge > > > ip link set tap0 up > > > qemu-kvm -hda debian.img -cpu host -m 512 -vnc :0 \ > > > -net nic,model=virtio,macaddr=02:02:02:02:02:02 \ > > > -net tap,fd=3 3<>/dev/tap$(< /sys/class/net/tap0/ifindex) > > > > > > on one physical host which is otherwise completely idle. From a second > > > physical host on the same network, I then scp a large (say 50MB) file onto > > > the new guest. On a gigabit LAN, speeds consistently drop to less than > > > 100kB/s as the transfer progresses, within a second of starting. > > > Thanks for the report. > > I'll try to reproduce this early next week. > > Meanwhile a question - do you still observe this behaviour if you enable > > vhost-net? > > I haven't tried running with vhost-net before. Is it sufficient to compile > the host kernel with CONFIG_VHOST_NET=y and boot the guest with > > qemu-kvm -hda debian.img -cpu host -m 512 -vnc :0 \ > -net nic,model=virtio,macaddr=02:02:02:02:02:02 \ > -net tap,fd=3,vhost=on,vhostfd=4 \ > 3<>/dev/tap$(< /sys/class/net/tap0/ifindex) 4<>/dev/vhost-net > > ? If so, then I'm afraid this doesn't make any difference: it still stalls > and drops right down in speed. > > The reason I'm hesitant about whether the vhost-net is actually working is > that with both vhost=off and vhost=on, I see an identical virtio feature set > within the guest: > > # cat /sys/bus/virtio/devices/virtio0/features > 0000011000000001111100000000100000000000000000000000000000000000
Yes that is expected. > However, without the 4<>/dev/vhost-net or with 4<>/dev/null, it seems to > fail to start altogether with vhost=on,vhostfd=4, so perhaps it's fine? > > Cheers, > > Chris.
