A friend of mine forwarded a mail from the LOPSA mailing list about tuning VMs running on KVM/libvirtd to make them more responsive. As I use puppet to manage my own VMs, a file and a new class later, I have edited /etc/default/grub to add elevator=deadline to the options, then run update-grub. You will obviously need to reboot your VM for this to take effect. I’ll report in a few days with some graphs.