I am very new to HyperV and virtual machine philosophy in general, so please expect more or less nooby questions :)

I have a server that is only used as a host for virtual machines. OS is windows server 2008 R2 and it is running on 16 CPU and 48 GBs of RAM.

On aforementioned server there are 8 VMs, each having 4 CPUs and 4 GBs of RAM. On those VMs we are running some CPU intensive tasks. Each machine has nearly 100% cpu usage. After I noticed slow performance I went to the host machine and started playing with process explorer. It turned out that cpu usage is very low. Also I/O is very low, and of course, memory consumption is high, which is expected.

Of course, I don't expect that those 4 virtual cores dedicated to a VM work as fast as real, hardware 4 cores, but still I expected a higher consumption of real hardware.

Is this sort of behaviour normal? I see that the most of CPU usage on host machine are marked as interrupts (which I guess is normal) and all those interrupts are passed to only one core (which is strange). Are there out of box optimization that I could perform to finally use all that processing power that is under the hood.

My knowledge of virtualization technology is near to embarrassing, so I would be grateful for any links that could enlightened me :)

Thanks.