PRM Product Overview

Figure 3. PRM groups based on pSets

Limiting maximum CPU consumption

For pSet PRM groups, CPU use is automatically restricted to (capped at) the number of cores in the

group.

For FSS PRM groups, there are two forms of capping:

• For all FSS PRM groups in the configuration—Each FSS PRM group can use only up to its

entitlement, regardless of whether additional CPU cycles are available. (The entitlement, or

guaranteed minimum, becomes a guaranteed maximum.)

• On a per-group basis (Available for HP-UX 11i v3 and later)—You set a cap for only those FSS

PRM groups for which you want to cap CPU consumption. You cap these groups at or above their

entitlement values.

Capping is useful for setting and controlling users’ or applications’ expectations of system

performance. For example, a shared system could be configured so users always see the same

response time, regardless of the load on the system. The CPU capping feature is particularly useful

during the process of consolidating multiple applications onto a single server. Initially, only one

application may be running on that server, and users experience exceptionally fast response times.

Later, when more applications are added to the server, the users of the first application could

experience a decrease in performance, resulting in problem reports. By capping resource allocation

to applications from the start, you prevent such performance problem perceptions.

CPU capping is also useful to “contain” resource-intensive applications (such as a CPU-bound

program), applications that might have gone into a bad state (for example, infinite loop) or

applications that are poorly written. CPU capping ensures that these applications cannot starve

critical applications on the system.

Managing private real memory allocation

Applications need access to private real memory to perform their jobs. Contention for private memory

can affect application performance. IT managers who are considering application consolidation want

to be assured that their applications will not experience performance degradation caused by memory

contention with other applications on the system.

Without PRM, critical applications could have their memory paged out in favor of lower priority

applications or applications that might already be consuming too much memory.

The PRM memory manager complements the standard HP-UX memory manager by prioritizing

processes. This prioritization is performed according to the memory shares assigned to the PRM

PRM Group A

(pSet 0)

PRM Group B

(pSet 1)

PRM Group C

(pSet 2)

emory

Application A

Application B

Application C