HP Process Resource Manager User's Guide

Understanding how PRM manages resources
How PRM manages real memory resources
Chapter 2 51
As implied above, PRM provides a PRM group its entitlement on a
symmetric-multiprocessing (SMP) system with Hyper-Threading
disabled by granting the group its entitlement on each core. If the group
does not have at least one process for each core, PRM compensates by
proportionally increasing the PRM group’s entitlements on cores where
it does have processes. For example, a PRM group with a 10%
entitlement on a 4-core system, gets 10% of each core. If the group is
running on only one core because it has only one process, the 10%
entitlements from the three unused cores are given to the group on the
core where it has the process running. Thus, it gets 40% on that one core.
NOTE A PRM group on a system with Hyper-Threading disabled may not be
able to get its entitlement because it has too few processes. For example,
if the PRM group above—with only one single-threaded process—were to
have a 50% entitlement for the 4-core system, it would never get its
entitlement. PRM would give the group an entitlement of 100% on two
cores. However, because the group has only the one thread, it can use
only one core—resulting in a 25% entitlement.
How PRM manages real memory resources
Memory management refers to the rules that govern real and virtual
memory and allow for sharing system resources by user and system
processes.
In order to understand how PRM manages real memory (both private
and shared), it is useful to understand how PRM interacts with standard
HP-UX memory management.
How HP-UX manages memory
The data and instructions of any process (a program in execution) must
be available to the core by residing in real memory at the time of
execution. Real memory is shared by all processes and the kernel.