Hyper-V VM Details Test

While the test reports a wide variety of other metrics too for virtual machines that are alive, only the Powered on status is indicated for virtual machines that are currently not available.

If this measure reports the value On, it indicates that the guest is up and running. The value Off could indicate that the guest has been powered-off; it could also indicate that the guest has moved to a different Hyper-V server.

The numeric values that correspond to each of the powered-on states discussed above are listed in the table below:

Note:

By default, this measure reports the values On or Off to indicate the status of a VM. The graph of this measure however, represents the status of a VM using the numeric equivalents - 0 or 1. 

All execution in the root and child partitions (where guest VMs run) happens on Virtual Processors (VPs).  At a minimum, you will see one VP for each Logical Processor (LP).  These account for the root VPs.  You will then see one for each VP you have configured to a guest.  Therefore, if you have an 8LP system with 1 guest running with 2 VPs, the count here will be 10.

This measure serves as an effective indicator of how resource-intensive a particular VM is on a specific Hyper-V server.

Comparing the value of the Virtual machine runtime and Hypervisor runtime measures for every VM will reveal where the virtual processors of the VM have spent more time – in processing guest code or in processing hypervisor code?

Ideally, this value should be very low. A high value could be indicative of a network bottleneck.

These measures are good indicators of the activity on the disks attached to the IDE controller.

For each partition, the hypervisor maintains a memory pool of RAM SPA pages. This pool acts just like a checking account. The amount of pages in the pool is called the balance deposited or withdrawn from the pool. When a hypercall that requires memory is made by a partition, the hypervisor withdraws the required memory from the total pool balance of that partition. When the balance available in the pool is less, then more memory pages are deposited in the pool.

A very high value of this measure therefore, indicates that the balance in the pool maintained for this partition is dwindling. This is a cause for concern.

Hypercalls are one form of enlightenment.  Guest OS’s use the enlightenments to more efficiently use the system via the hypervisor. TLB flush is an example hypercall. If this value is zero, it is an indication that Integration Components are not installed.  New OS’s like WS08 can use hypercalls without enlightened drivers. So, hypercalls are only a prerequisite and not a guarantee for not having Integration Components installed.

Control registers are used to set up address mapping, privilege mode, etc.

A HLT will cause the hypervisor scheduler to de-schedule the current VP and move to the next VP in the runlist.

The MWAIT (monitored wait) instruction instructs the processor to enter a wait state in which the processor is instructed to monitor the address range between a and b and wait for an event or a store to that address range.

The CPUID instruction is used to retrieve information on the local CPU’s capabilities. Typically, CPUID is only called when the OS / Application first start. Therefore, this value is likely to be 0 most of the time.

Whenever guest code accesses a page not in the CPU TLB a page fault will occur. This counter is closely correlated with the Large Page TLB Fills measure.

Whenever a guest VP needs to exit its current mode of running for servicing in the hypervisor, this is called an intercept.  Some common causes of intercepts are resolving Guest Physical Address (GPA) to Server Physical Address (SPA) translations, privileged instructions like hlt / cupid / in / out, and the end of the VP’s scheduled time slice.

There are two types of TLB entries (and some three).  Small TLB which generally means a 4K page and large Page which generally means 2MB.  There are fewer Large TLB entries on the order of 8 – 32.

A non-zero value for this measures indicates that the root partition is using large pages. 

There are two types of TLB entries (and some three).  Small TLB which generally means a 4K page and large Page which generally means 2MB.  There are fewer Large TLB entries on the order of 64 – 1024+.

Comparing the value of this measure across VMs will enable you to accurately identify the VMs on which CPU-intensive applications are executing. 

Since VMs are easy to create and deploy, many a time an administrator might be faced with scenarios where many VMs are created on an Hyper-V host, but very few are actively used. A VM, whether powered on or off, consumes disk space on a host. When the Hyper-V server hosting the VMs runs low on disk space, administrators might want to know which VM is taking up maximum disk space. This measure reveals the disk capacity of a VM, regardless of its on/off state. A quick comparison of the capacity across VMs can enable administrators to accurately identify the VM that is taking up maximum disk space.

Compare the value of this measure across VMs to know on which VM I/O activity was abnormally high.

Compare the value of this measure across VMs to know on which VM network I/O activity was abnormally high.

If the value reported by this measure is 1, the status is Ok.

If the value reported by this measure is 3, the status is Critical.

The Detailed Diagnosis (DD) of this measure shows the VM State, Process ID, and Operational Status.

The values of these measures should typically be low. The more time a VM spends waiting to run, the more lag time there is in responsiveness within the VM.