HP Process Resource Manager User's Guide

Understanding how PRM manages resources
How PRM manages real memory resources
Chapter 258
At Time A
• There is plenty of memory available on the system for the processes
that are running.
• Group1 is using its share, and Group2 is using slightly more than its
share, borrowing excess from Group3.
• Group3 is using much less than its share.
At Time B:
• System memory use approaches 100%.
• Group1 is borrowing excess memory from Group3.
• Group2 processes reach the group’s 30% memory cap. Consequently,
Group2’s processes are forced to page, causing a performance hit.
Between Time B and Time C, Group3’s demands continue to increase.
At Time C:
• System memory use is near 100%.
• Group3 is not getting sufficient memory and needs its loaned-out
memory back. PRM then determines which groups are overachieving
with respect to their memory entitlement. In this case, the
increasing demand of Group3 causes Group1 and Group2 to be pulled
toward their shares of 30% and 10% respectively despite their desire
for more memory. Group3 is allowed to freely consume up to 60% of
available memory, which it reaches at Time D.
After Time D:
PRM now holds each group to its entitled memory percentage. If a group
requests more memory, the request is filled with pages already allocated
to the group.