What exactly is the CPU Average field in VMM 2012 showing me?

I'm running Server 2008 R2 with VMM 2012. My server has 2x16 core CPUs installed.

An example virtual machine has 4 virtual processors, and shows 20% CPU usage. Is that:

  • 20% of the entire system's available CPU power?
  • 20% of 4 of the 32 core's CPU power?
  • 20% of one core's CPU? (in which case it could go as high as 400%)
  • Something else entirely?

How can I tell how much of the entire system's CPU power is being used (all 32 cores)?

Edit: Well, I can tell for sure it's not 20% of the entire system's CPU power - since the entire server's CPU averages add up to well over 100% right now.

  • I can only answer this at a guess, but generally CPU usage reporting at a hypervisor is of its allocated resources. So if you have assigned 1 vCPU then it's 20% of that. (i.e. your 2nd option). Same with its RAM usage, it's only the % of allocated RAM, not the total system RAM. – Mark Henderson Nov 20 '12 at 3:40
  • On further investigation I think that it's on drugs. I did a test and loaded a VM with Prime95 to load up its entire CPU allocation. In the Hyper-V console I see 12% (which is the total allocation/total available), indicating that it's showing the total used out of the entire system. But SCVMM is showing 0%. So I don't know what to make of that... – Mark Henderson Nov 20 '12 at 4:05
  • I've asked another question to try and nut it out: serverfault.com/questions/450352/… – Mark Henderson Nov 20 '12 at 4:20
  • Very much agreed that vmm is on drugs...but I still want to know what it thinks it is reporting :) So if I open Hyper-V manager on the vm server, 100% on a 4 proc VM means 100% of the 4 assigned cores, correct? – Grant Nov 22 '12 at 0:37
  • This article seems relevant: blogs.technet.com/b/scvmm/archive/2010/04/07/… if you want to test if what it says is accurate – Grant Nov 22 '12 at 0:40

For a Hyper-V guest, the VMM console shows CPU Average as the “%Guest Run Time” counter of “Hyper-V Hypervisor Virtual Processor(_Total)” counter set. This also relates to any limit in percent set on the Processor setting under settings for the Hyper-V guest.

E.g. If you have a guest with a 4 core CPU and 50% VM limit and the utilization as shown from inside the guest OS is 100%, the VMM console would show this as about 50%. However, if you look in the Hyper-V console it would show about 25% as the Hyper-V console relates to the host CPU usage (the host in this example would have 8 cores).

Source: How SCVMM Determines CPU Average Displayed in the Admin Console

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