Did anyone ever try that? I just figured it might worthwhile to offline unused CPUs in Xen hosts instead of letting them twiddle their toes at 800MHz or more.
for node in $nodes ; do
ssh-copy-id -i /root/.ssh/id_dsa_xenhost $node
ssh $node "echo 0 > /sys/devices/system/cpu/cpu1/online"
for node in $nodes Domain-0; do
xm vcpu-pin $node all 0
done && echo 0 > /sys/devices/system/cpu/cpu1/online