Introduction

The performance of various workload types running in a set of virtual systems under z/VM® was evaluated. During these evaluations, the amount of processors and the amount of memory available to the z/VM host system were constrained.

The set of workloads was initially optimized in an unconstrained environment, and the resulting configurations were kept constant for all performed tests. This includes that the configuration of the virtual systems – such as the number of virtual processors, the relative shares and the amount of virtual memory – was kept constant as well.

For subsequent test executions, the number of real CPUs and the amount of real memory available to the z/VM host system were iteratively reduced, creating processor or memory shortages, or both, in the z/VM host system. The reductions were carried forward with each test iteration, until workload errors were encountered.

The resource shortages in z/VM had implications on the performance of the various workloads running under Linux™ within virtual systems. Meaningful metrics were identified and monitored to determine the impact of the z/VM resource shortages on the workload performance, compared to the initial unconstrained environment.