HP-UX Workload Manager User's Guide

Introduction
What is HP-UX Workload Manager?
Chapter 1 43
feature for PSET-based groups. WLM automatically sets the
Hyper-Threading state for the default PSET to optimize performance.
(The default PSET, also known as PSET 0, is where all FSS groups
reside.) When new PSETs are created, they inherit the Hyper-Threading
state that the system had before WLM was activated (inheritance is
based on the system state prior to WLM activation because WLM may
change the Hyper-Threading setting for the default PSET to optimize
performance). Cores can be moved from one partition to another and will
take on the Hyper-Threading state of their destination PSET. To
explicitly enable or disable Hyper-Threading for a PSET-based group,
thereby overriding the default state for cores assigned to that group,
specify the LCPU keyword with the PSET group definition in the prm
structure. You can also modify the Hyper-Threading state of the system.
For more information, see “Specifying workload groups (optional)” on
page 159 and wlmconf(4).
Workload management across partitions
WLM is optimized for moving cores across hosts such as nPartitions and
virtual partitions. Using hosts as workloads, WLM manages workload
allocations while maintaining the isolation of their HP-UX instances.
WLM automatically moves (or “virtually transfers”) cores among
partitions based on the SLOs and priorities you define for the workloads.
With virtual partitions, WLM can automatically balance resources across
the partitions. For example, if a processor is not being utilized within one
virtual partition, WLM can deallocate it and reassign it to an alternate
virtual partition that currently requires additional resources.
With nPartitions, the cores are not physically moved. Instead, HP
Instant Capacity software (formerly known as iCOD) simulates the
movement of cores between partitions by deactivating cores on one
nPartition, then activating cores on another nPartition. For information
on managing SLOs across partitions, see Chapter 7, “Managing SLOs
across partitions,” on page 255.
WLM can manage nested workloads (based on FSS groups and PSETs)
inside virtual partitions that are inside nPartitions. Information on
nested management is provided in Chapter 8, “Management of nested
nPars / vPars / workload groups,” on page 277.
For each host (nPartition or virtual partition) workload, you define one or
more SLOs in the WLM configuration file. WLM allows you to prioritize
the SLOs so that an SLO assigned a high priority is given precedence