Dietmar Maurer wrote: >> > ./x86_64-softmmu/qemu-system-x86_64 -smp sockets=1,cores=2 -m 512 - >> hda >> > debian-squeeze-netinst.raw -netdev >> > type=tap,id=net0,ifname=tap111i0,vhost=on -device >> > virtio-net-pci,netdev=net0,id=net0 >> > >> > Downloading a larger file with wget inside the guest will show the >> problem. >> Speed drops from 100MB/s to 15MB/s. >> > >> > Can someone reproduce that bug? Any ideas how to fix that? >> >> Which exact QEMU are you using: qemu or qemu-kvm? Distro package or >> from source? Any patches applied? > > I just tested with latest sources from git://git.qemu-project.org/qemu.git > > ./x86_64-softmmu/qemu-system-x86_64 -smp sockets=1,cores=2 -m 512 -hda > debian-squeeze-netinst.raw -netdev > type=tap,id=net0,ifname=tap111i0,vhost=on -device > virtio-net-pci,netdev=net0,id=net0 --enable-kvm > > got incredible bad performance - can't you reproduce the problem?
I have seen a similar problem, but it seems to be only with extreme old guest kernels. With Ubuntu 12.04 it seems not to be there. Can you try a recent guest kernel.