HP Process Resource Manager User's Guide

Understanding how PRM manages resources
How PRM manages real memory resources
Chapter 254
When system memory use is at 100%, borrowed memory pages are
returned to the owning PRM groups if needed. The time involved for the
borrowed memory pages to be returned is dependent on the swap rate
and the order in which old pages are paged out.
If a group is exceeding its memory shares on a system that is paging,
prm2d uses proportional overachievement logic. Overachievement for a
group is the ratio of memory used to memory entitlement. This value is
then compared to the average overachievement of all groups. If a PRM
group is overachieving compared to the average, then the number of
import pages for that group is reduced. This allows other groups to start
importing the newly available memory.
Groups are not allowed to exceed their memory caps.
NOTE When an initial configuration requesting memory management is loaded
(after installing or resetting PRM), PRM initializes memory resource
groups (MRGs) giving all usable memory to PRM_SYS initially. Any free
memory is then distributed to other PRM groups. This distribution of
memory for use by your PRM groups can be affected by:
• Heavy paging or swapping
• A single application using over half the lockable memory on the
system
Such conditions may exist if memory-intensive applications start
immediately after PRM is configured—as may be the case with
applications starting automatically at reboot.
You can possibly avoid these issues by:
• Starting these applications in their designated PRM groups with the
prmrun command
• Using the PRM_SLEEP variable in your /etc/rc.config.d/prm file so that
the application manager and memory manager can place processes
in their configured groups before the heavy demand begins.