HP Process Resource Manager User's Guide

Understanding how PRM manages resources
How PRM manages CPU resources
Chapter 244
Because the rate at which the priority increases is slowest when CPU
load is high, the result is that a process with a heavy demand for CPU
time is penalized by the standard HP-UX scheduler as its CPU resource
use increases.
With PRM, you can reverse the effects of the standard scheduler. By
placing users with greater demands for CPU resources in an FSS PRM
group with a higher relative number of CPU shares than other groups,
you give them a higher priority for CPU time. In a similar manner, you
can assign an application to an FSS PRM group with a higher relative
number of shares. The application will run in its assigned FSS PRM
group, regardless of which user invokes it. This way you can ensure that
critical applications have enough CPU resources. You can also isolate
applications and users with greater demands for CPU resources by
placing them in a PSET PRM group and assigning the desired number of
cores to the group. The applications and users will have dedicated access
to the cores in the PSET PRM group, ensuring CPU cycles when needed.
This method of isolating applications and users effectively creates a
partition on your system.
PRM manages CPU resources by using the fair share scheduler (FSS) for
FSS PRM groups. When the PRM CPU manager is enabled, FSS runs for
FSS PRM groups instead of the HP-UX standard scheduler. When PSET
PRM groups are configured, FSS still runs for FSS PRM groups, but the
standard HP-UX scheduler is used within PSET PRM groups.
PRM gives higher-priority FSS PRM groups more opportunities to use
CPU time. Free CPU time is available for use by any FSS PRM group
and is divided up between FSS PRM groups based on relative number of
CPU shares. As a result, tasks are given CPU time when needed, in
proportion to their stated importance, relative to others with a demand.
PRM itself has low system overhead.