HP-UX Workload Manager User's Guide

Configuring WLM
Defining the PRM components (optional)
Chapter 5 179
extra CPU resources to go to your workload groups, set the
distribute_excess tunable in your configuration file. This tunable is
described in the section “Distributing excess CPU resources to your
workloads (optional)” on page 218. If you do not set this tunable, all the
excess CPU resources go to the default workload group OTHERS.
To specify a group’s CPU weight, use the weight keyword in the prm
structure, according to the following syntax:
weight = group : wt [, ...];
where
group Is the workload group name.
wt Is group’s CPU weight. The value must be an integer
greater than or equal to 1. The default weight for a
group is 1.
NOTE Weighting a group is beneficial only if the group is going to have an
active SLO.
When resources are insufficient to satisfy a demand at a given priority,
WLM uses weighting to determine how to distribute CPU resources
among the requests at that priority. WLM attempts to allocate resources
so that the weight-to-allocation ratio is the same for all the groups.
However, to determine the CPU allocations, WLM first observes the
following constraints:
• A group’s CPU allocation must not exceed the SLO request unless all
SLOs at the same priority are satisfied.
• Any CPU allocation mandated by a group’s higher-priority SLO is
always retained (it is never reduced to achieve a weight-to-allocation
ratio that equals that of the other groups at the same priority level,
as sought under normal circumstances).
This policy for determining allocations also applies to CPU demand that
is not a direct result of a prioritized SLO, such as gmincpu values and
distribution of excess (when the distribute_excess tunable is set). The
ultimate consequence of this policy is that, in the absence of other SLO
requests, two requests at the same priority level that are not fully
satisfied will have the same ratio between their respective allocations as