The “Hyper-V Hypervisor Virtual Processor” and “Hyper-V Hypervisor Root Virtual Processor” counter sets have the same counters. The only difference between the two is the ““Hyper-V Hypervisor Root Virtual Processor” contains counters for only the Root Virtual Processors (VP’s) whereas “Hyper-V Hypervisor Virtual Processor” has counter for all other partitions.

The virtual processor counters are very useful because they help you understand how much guest VM’s are running and where they are running. Unfortunately these counters do suffer from a small amount of clock skew in WS08 Hyper-V but this only slightly reduces their usefulness. We hope to remove the clock skew in future releases. The skew shows up in that some” %” counters may exceed 100%. I’ve seen some go as much as 110% depending on the system load. The problem has to do with the fact this counter set uses the clock from the root rather than from the hypervisor as a basis of time. For more on clock skew see (http://blogs.msdn.com/tvoellm/archive/2008/03/20/hyper-v-clocks-lie.aspx).

Virtual Processors (VP) are the unit of execution for a partition and each partition contains one guest virtual machine (VM). For each VP there is a set of counters. Perfmon.exe will let you view the counters separately or as an average for all VP’s called “_Total”. VP counters are prefixed with the name of the partition like this “WS08 Guest 1:” followed by the VP id like this “Hv VP 0”. This makes it easy to identify which VP’s go with which partitions.