HP-UX Workload Manager User's Guide

Configuring WLM
Trying a configuration without affecting the system
Chapter 5240
rely on prmlist or prmmonitor to observe changes when using passive
mode. These utilities will display the configuration WLM used to create
the passive mode. However, you can use prmmonitor to gather CPU
usage data.
The effect of passive mode on usage goals and metric goals
As noted previously, in passive mode, the WLM feedback loop is not in
place. The lack of a feedback loop is most dramatic with usage goals.
With usage goals, WLM changes a workload’s CPU allocation so that the
group’s actual CPU usage is a certain percentage of the allocation. In
passive mode, WLM does not actually change CPU allocations. Thus, an
SLO with a usage goal might be failing; however, that same SLO might
easily be met if the feedback loop were in place. Similarly, an SLO that is
passing might fail if the feedback loop were in place. However, if you can
suppress all the applications on the system except for the one with a
usage goal, wlminfo should give you a good idea of how the usage goal
would work under normal WLM operation.
Passive mode can have an effect on SLOs with metric goals as well.
Because an application is not constrained by WLM in passive mode, the
application might produce metric values that are not typical for a normal
WLM session. For example, a database application might be using most
of a system. As a result, it would complete a high number of transactions
per second. The database performance could be at the expense of other
applications on the system. However, your WLM configuration might
scale back the database’s access to resources to allow the other
applications more resources. Thus, the wlminfo output would show
efforts to reduce the database’s CPU allocation. Because passive mode
prevents a reduction in the allocation, the database’s number of
transactions per seconds (and system use) remains high. WLM, believing
the previous allocation reduction did not produce the desired result,
again lowers the database’s allocation. Thus, with the removal of the
feedback loop, WLM actions in passive mode do not always indicate what
it would do normally.
Because of these discrepancies, always be careful when using passive
mode as an indicator of normal WLM operation. Use passive mode to see
trends in WLM behavior—with the knowledge that the trends may be
exaggerated because the feedback loop is not present.