PAL and virtualization

Mar 19, 2010 at 2:19 AM

Just curious to know if anyone has used PAL with virtualization like to analyze performance log data taken from virtual machines (VMWare, Virtual Server/PC, Xen, Amazon EC2, etc.).

I know and anticipate some of the performance data may not be accurate when captured from virtual machines. At least on Amazon EC2, what appears to be unaccurate are CPU utilization and processor queue length. But others like memory used (private bytes) seem to be realistic when profiling a known test application under both virtual machine and physical machine for comparison.

Mar 31, 2010 at 8:40 AM

I have a Hyper-V threshold file in PAL to analyze the host machine because you need to look at the "\Hyper-V Hypervisor Logical Processor(*)\% Total Run Time" to see what the physical processor are doing. Task Manager on the host and % Processor Time are only measuring the Root Partition. Think of the host operating system as another virtual machine that happens to be special.

Yes, virtual machines tend to have high processor queue lengths with low CPU utilization. This is known and is not an indicator of a problem. It is the way the that counter is collected that makes it inaccurate.

Anything that uses a percentage like % Processor Time will be slightly skewed on virtual machines, but typically it's within 10 to 20% deviation.

Other than that, I analyze virtual machines just like any other.

Mar 31, 2010 at 6:30 PM

Thanks for the feedback Clint. They'll be helpful to me.