The difference between REAL and Virtual CPU

Products

• Explore Performance Management for z/VSE

Issue/Introduction

What is the difference between REAL and Virtual CPU?

Occasionally the virtual CPU shows 100%.  Is that the total including VM or is it just the portion that z/VSE gets from VM?

 

Resolution

VSE CPU %REAL = Actual cpu time divided by Total wall clock duration time.

VSE CPU %BUSYV = Actual cpu time divided by Virtual duration time.
Virtual duration time = Amount of time VSE was not dispatched if running under VM.

Example:
If VSE is busy for 5 minutes during 15-minute time interval and not dispatched for 10 minutes, then
%REAL = 5/15 = 33%
%VIRTUAL = 5/5 = 100%