HP Process Resource Manager User's Guide

Understanding how PRM manages resources
How PRM manages CPU resources
Chapter 248
NOTE Capping based on the CPUCAPON mode overrides per-group capping;
however, using both forms of capping at the same time is not
recommended.
For PSET PRM groups, capping is a result of the number of cores
assigned to the group.
Capping CPU usage can be a good idea when migrating users and
applications to a new system. When the system is first introduced, the
few users on the system may become accustomed to having all of the
machine’s resources. However, by setting CPU caps early after the
system’s introduction, you can simulate the performance of the system
under heavier use. Consequently, when the system becomes more heavily
used, performance is not noticeably less. For information on capping
CPU resource use, see “Specifying PRM groups/controlling CPU resource
use” on page 104.
How PRM manages CPU resources for real-time
processes
Although PRM is designed to treat processes fairly based upon their
assigned shares, PRM does not restrict real-time processes. Real-time
processes using either the POSIX.4 real-time scheduler (rtsched) or the
HP-UX real-time scheduler (rtprio) keep their assigned priorities
because timely scheduling is crucial to their operation. Hence, they are
permitted to exceed their group’s CPU share and cap. The CPU resources
they use are charged to their groups. Thus, they can prevent other
processes in their groups from running.