There are a number of groups building management software (OEMs, Microsoft, …) for Hyper-V which is cool to see.  A common ask from these teams has been around reading and computing VM CPU usage.

The following is an example of how to compute Hyper-V guest processors usage.  You can use the same formula for “% Total Run  Time, “% Hypervisor Time” and “% Idle time”.   The counters show up in the Win32_PerfRawData_HvStats_HyperVHypervisorLogicalProcessor WMI object asPercentGuestRunTime”, “PercentTotalRunTime”, “PercentHypervisorRunTime”, and “PercentIdleTime”.

To make the formula easier to read lets use:

                GN – Percent Guest Run Time (substitute other usage values here)

                PN – Timestamp_PerfTime

                FN – Frequency_PerfTime

                LP = Number of logical processors (Get this from the “Hyper-V Hypervisor” counterset)

 

                         F1 * (G2 – G1)

 Utilization =  -----------------------------------

                     100000 * LP * (P2-P1)

 

G2 and P2 are the second values read and G1 and P1 are the first values read.

To test the formula lets read the “Hyper-V Hypervisor Logical Process” counterset twice via the Win32_PerfRawData_HvStats_HyperVHypervisorLogicalProcessor WMI object about 10 seconds apart with a single VM running at 100% Guest CPU.  Since my test machine has two CPU’s (2 LP) this means we should see about 50% overall utilization.

V:\backup>winrm enum wmi/root/cimv2/* -filter:"select * from Win32_PerfRawData_HvStats_HyperVHypervisorLogicalProcessor where name='_Total'"

Win32_PerfRawData_HvStats_HyperVHypervisorLogicalProcessor

    C1TransitionsPersec = 409197889

    C2TransitionsPersec = 0

    C3TransitionsPersec = 0

    Caption = null

    ContextSwitchesPersec = 889911109

    Description = null

    Frequency_Object = 0

    Frequency_PerfTime = 14318180

    Frequency_Sys100NS = 10000000

    HardwareInterruptsPersec = 92282462

    InterProcessorInterruptsPersec = 8174254

    InterProcessorInterruptsSentPersec = 8174254

    MonitorTransitionCost = 16

    Name = _Total

    PercentC1Time = 4193635539355

    PercentC2Time = 0

    PercentC3Time = 0

    PercentGuestRunTime = 314976793671

    PercentHypervisorRunTime = 53745475789

    PercentIdleTime = 8385447570540

    PercentTotalRunTime = 368722269460

    SchedulerInterruptsPersec = 384836664

    TimerInterruptsPersec = 33425466

    Timestamp_Object = 0

    Timestamp_PerfTime = 6268633722843

    Timestamp_Sys100NS = 4199325031975

    TotalInterruptsPersec = 518718846

 

V:\backup>winrm enum wmi/root/cimv2/* -filter:"select * from Win32_PerfRawData_HvStats_HyperVHypervisorLogicalProcessor where name='_Total'"

Win32_PerfRawData_HvStats_HyperVHypervisorLogicalProcessor

    C1TransitionsPersec = 409201218

    C2TransitionsPersec = 0

    C3TransitionsPersec = 0

    Caption = null

    ContextSwitchesPersec = 889922035

    Description = null

    Frequency_Object = 0

    Frequency_PerfTime = 14318180

    Frequency_Sys100NS = 10000000

    HardwareInterruptsPersec = 92283571

    InterProcessorInterruptsPersec = 8174425

    InterProcessorInterruptsSentPersec = 8174425

    MonitorTransitionCost = 16

    Name = _Total

    PercentC1Time = 4193667417779

    PercentC2Time = 0

    PercentC3Time = 0

    PercentGuestRunTime = 315044817737

    PercentHypervisorRunTime = 53746578312

    PercentIdleTime = 8385511363951

    PercentTotalRunTime = 368791396049

    SchedulerInterruptsPersec = 384840537

    TimerInterruptsPersec = 33426627

    Timestamp_Object = 0

    Timestamp_PerfTime = 6268728855292

    Timestamp_Sys100NS = 4199364353043

    TotalInterruptsPersec = 518725160

 

Based the formula above and the data below we get = 51% which is spot on.

  Enjoy,

    Tony Voellm