Tim Magnan has released a free monitoring tool for Hyper-V environments called HyperV_Mon, currently in version 1.8. HyperV_Mon is a Gui tool for viewing CPU performance of a system running Microsoft Hyper-V. The tool can be downloaded from the Tmurgent Technologies website.
Although the tool isn’t intended as a regular monitoring tool, it can quickly help to understand what is going on at a Hyper-V host. The tool requires the .NET framework version 3.5 to be installed on the machine where you wish to start the GUI, and it leverages the Root Partition WMI provider of the server running Hyper-V. Further information about how to configure and use the tool is provided in the HyperV_Mon whitepaper.
"…With this tool, it is easy to understand why Windows XP and earlier OSs significantly underperforms on Hyper-V in comparison to Windows Server 2003, or Vista, or above. You will see significantly more hypervisor “overhead” processing with the older operating systems because Microsoft made modifications to the newer operating systems to be hypervisor (and processor VT) aware. Those newer OSs do not display such behavior. It is all in the enlightenments!…"