Why does the Task Manager does not show any activity from Hyper-V?

I've installed a Hyper-V role onto my Windows 2008 R2 Server. I have a bunch of VMs cranking at full speed, but the Task Manager on the host doesn't show any CPU activity from the VMs.

This kind of makes it difficult to quickly gauge the overall business of the host box and is annoying.

Is there an option somewhere either in the UI or registry or wherever else for the Task Manager to include the CPU Usage from the VMs?

Hyper-V is not something that runs within Windows. It's a bare metal Hypervisor. The OS that used to be installed on the machine is actually now a VM. It's a special VM in that it has direct access to the hardware, doesn't show up in Hyper-V's management console, and other such; but it's still now a VM. So it doesn't get to see what the other machines are doing any more than they can see it.

Since Hyper-V still uses the base OS for servicing disk and network IO, you can pull those numbers from PerfMon. The Memory and Processor numbers obtains from PerfMon are skewed however and should be taken with a grain of salt.

You need to use Performance Monitor. The counters also can only be seen from the Host operating system (not the other vm's).

Here is a specific article on the subject from Microsoft.