HP Process Resource Manager User's Guide

Understanding how PRM manages resources
How PRM manages real memory resources
Chapter 2 55
Reducing memory shares
If a PRM group’s memory share is reduced while the group is using most
of its memory pages, the reduction is not immediately visible. The
memory must be paged out to the swap device. The time involved for the
reduction to take effect is determined by the memory transfer rate (for
example, 2 Mbytes/second), and the order in which the old pages are
paged out.
Therefore, when changing shares, give them time to take effect before
implementing new shares again.
Capping memory use
You can optionally specify a memory cap for a PRM group. This cap is a
hard upper bound: a PRM group cannot exceed its memory cap.
Typically, you might choose to assign a memory cap to a PRM group of
relatively low priority, so that it does not place excessive memory
demands on the system. For information on setting a memory cap, see
“Controlling memory use” on page 113.
Implementation of shares and caps
In addition to specifying memory shares (a lower bound) for private
memory, you can optionally specify a memory cap (upper bound) for a
PRM group.
It is important to note the difference between memory shares and a
memory cap. Shares guarantee the minimum amount of real memory
that a group is allowed to consume at times of peak system load. The
memory cap is an upper bound.
Isolating a group’s private memory resources
In addition to specifying private memory shares, the prm2d memory
manager allows you to optionally specify a group’s private memory
resources to be restricted from use by other groups and processes on the
system. This type of restriction is called memory isolation.
When a group’s memory shares are isolated, those memory shares
cannot be loaned out to other groups. Memory isolation also means that
memory cannot be borrowed from other groups.