A very useful note from a blog I have now lost the link for (sorry anonymous blogger) on ensuring the vhost_net module is loaded if you are running virtual machines with virtio, as it will shift some of the work from userspace to the kernel, which could reduce CPU load on the host machine for network and IO ops on the guest.

More info:

  • "Linux-KVM":http://www.linux-kvm.org/page/VhostNet
  • "http://lwn.net/Articles/346267/":http://lwn.net/Articles/346267/

(N.B. Possible problem with using DHCP and vhost_net)