Linux – Domain-0 high CPU load

Task Manager doesn't show total processor time, it only shows the root partition's processor time. Take a look at the following article for information on how to determine the aggregate / total processor usage:

See: http://blogs.msdn.com/tvoellm/archive/2009/04/23/monitoring-hyper-v-performance.aspx To Quote:

Processor:

Once you have an idea of the overall system capabilities and configuration though the “Hyper-V Hypervisor” counter set you will want to monitor the processors on the system. The most important counter set to monitor is the “Hyper-V Hypervisor Logical Processor”. This counter set allows you to determine how much of the physical processor are being used. The virtual processor counter sets only show a slice of the “Hyper-V Hypervisor Logical Processor”.

Hyper-V Hypervisor Logical Processor

Hyper-V Hypervisor Root Virtual Processor

Hyper-V Hypervisor Virtual Processor

Bjørn, you're worried about something that isn't an issue. In your case, you have a hypervisor and four virtual machines. One of those virtual machines (the management OS) came with the hypervisor. You then installed three virtual machines.

Ask yourself whether you'd like to see the management OS using CPU time. Ideally, you want it to leave as much CPU time as it possibly can to the three VMs that you set up.

This is exactly what Hyper-V does, assuming that you have installed the "VM Integration Components" in all your VMs. These components make I/O much more efficient by installing drivers that are meant for VMs. Then, unless your VMs are particularly I/O-heavy, your management OS will just sit there waiting for you to interact with it, attempting to use as few resources as possible. This is a good thing.

If you want to see the actual CPU metrics from the hypervisor, not the management OS, use Performance Monitor in the management OS and look for the Hyper-V counters. These will tell you about physical CPU usage.

Doug Luxem (who seems to know a lot about this) answered this well on another thread today. So I'll just steal his text:

First, you have to remember that in Hyper-V that the "host" is called a parent partition and it really just like a virtualized guest with special permissions and roles. Just like any other child/guest, when you open up Task Manager, you can not see the CPU usage of the other children on the server.

Ben Armstrong has a good explanation of this here: http://blogs.msdn.com/virtual_pc_guy/archive/2008/02/28/hyper-v-virtual-machine-cpu-usage-and-task-manager.aspx

Lastly, look at RAM usage in your VMs. Look at disk queue length. These will tell you if you need more RAM. It sounds, though, like your VMs just need more total CPU than the host has to give.