When running my guests with 'vhost=on', a lot less guest memory is available (about 18.5 MB less for each networking device). I searched the mailing list archive and found a comment by Michael S. Tsirkin: "with vhost, virtio does currently consume a bit more memory than with userspace backend" Is 18.5 MB per device the expected amount, and can I change some setting to reduce it? Here's the 'free' output of a guest with 7 tap devices (qemu-kvm 0.13.0, linux 2.6.36.2 host and guest): Started the guest with 'vhost=off': total used free shared buffers cached Mem: 253564 39260 214304 0 1732 15124 -/+ buffers/cache: 22404 231160 Swap: 409620 0 409620 Same guest, but with 'vhost=on': total used free shared buffers cached Mem: 253564 169092 84472 0 1744 15120 -/+ buffers/cache: 152228 101336 Swap: 409620 0 409620 The command that started the guest: /opt/kvm/bin/qemu-system-x86_64 \ -nographic \ -daemonize \ -cpu host \ -M pc-0.13 \ -m 256 \ -mem-path /hugepages \ -smp 2 \ -name gw \ -uuid d9d6332d-10ba-4cfa-925b-4e4d14f7cd86 \ -boot c \ -drive file=/opt/kvm/var/img/gw.raw,if=virtio,index=0,boot=on,cache=none \ -device virtio-net-pci,netdev=virtio.0,mac=fe:60:20:3a:8d:37 \ -netdev tap,id=virtio.0,ifname=gw-lan,script=no,downscript=no,vhost=on \ -device virtio-net-pci,netdev=virtio.1,mac=06:c8:4d:85:47:45 \ -netdev tap,id=virtio.1,ifname=gw-dmz,script=no,downscript=no,vhost=on \ -device virtio-net-pci,netdev=virtio.2,mac=e2:57:e2:6b:67:7c \ -netdev tap,id=virtio.2,ifname=gw-inet,script=no,downscript=no,vhost=on \ -device virtio-net-pci,netdev=virtio.3,mac=72:47:f5:4d:59:01 \ -netdev tap,id=virtio.3,ifname=gw-lanv,script=no,downscript=no,vhost=on \ -device virtio-net-pci,netdev=virtio.4,mac=02:de:c4:7b:71:6e \ -netdev tap,id=virtio.4,ifname=gw-dmzv,script=no,downscript=no,vhost=on \ -device virtio-net-pci,netdev=virtio.5,mac=fe:6a:ac:4e:16:f3 \ -netdev tap,id=virtio.5,ifname=gw-lanvpn,script=no,downscript=no,vhost=on \ -device virtio-net-pci,netdev=virtio.6,mac=7e:33:75:7a:ec:cd \ -netdev tap,id=virtio.6,ifname=gw-dmzvpn,script=no,downscript=no,vhost=on \ -serial unix:/opt/kvm/var/run/gw-serial.socket,server,nowait \ -monitor unix:/opt/kvm/var/run/gw-monitor.socket,server,nowait \ -parallel none \ -vga cirrus \ -runas kvm-gw -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
