VMRM Tuning Parameters

This section describes the Virtual Machine Resource Manager (VMRM) service virtual machine (SVM), the statements used to configure this SVM, and rules for adjusting users in a workload.

VMRM provides functions to dynamically tune the z/VM system. Groups of virtual machines can be defined to be part of a workload. The workloads can then be managed by VMRM to goals that are also defined. The system administrator can use VMRM to create a form of group scheduling for a set of virtual machines. There can be multiple workloads (groups of virtual machines), each managed to different goals. VMRM automatically adjusts performance parameters when there is contention between virtual machines for a resource. Therefore, VMRM is not effective in environments where resources are unconstrained.

Consider the following example. There are several virtual machines running web servers that are critical to the business. Another set of virtual machines are used by development and test groups that consume large amounts of resources. One workload could be defined that contains the virtual machines running the web servers and another workload that contains the development and test systems. Because the web serving workload is critical, the goals for this workload would be high. Lower goals could be created and assigned to the development and test workload. This example would ensure that development work would not interfere with business-critical workloads.

VMRM uses z/VM monitor data to obtain regular measurements of virtual machine resource consumption. Based on a customer-supplied definition of workloads and workload goals from a configuration file, VMRM will adjust virtual machine tuning parameters to achieve those goals.

Approximately once a minute (the recommended setting for the MONITOR SAMPLE interval) VMRM will compute the achievement levels for each workload. It selects a workload based on importance that is not within a reasonable percent of its CPU velocity goal (as described in GOAL Statement) to improve or degrade. If the workload has been selected recently for CPU velocity adjustment, VMRM skips it and attempts to select another one. VMRM then selects a workload that is not within a reasonable percent of its DASD velocity goal (as described in GOAL Statement) and adjusts the workload accordingly.