Active Memory Expansion Performance

All computers have a limited amount of Random Access Memory (RAM) in which to run programs. Therefore, one of the perennial design issues for all computer systems is how to make the best use of the entire RAM which is physically available in the system, in order to execute as many programs concurrently as possible, in the limited space available.

Active Memory Expansion, a POWER7™ feature, supplies a new technique for making better use of RAM: Portions of programs which are infrequently used are compressed into a smaller space in RAM. This, in turn, expands the amount of RAM available for the same or other programs.

This white paper describes the process of Active Memory Expansion in more detail in the next sections, and then reports measurements on a typical workload which illustrates the beneficial effects. Among the benefits of Active Memory Expansion, this paper shows the following scenarios and their performance results:

1. Reducing the physical memory requirement of an LPAR resulting in 111% memory expansion
2. Increasing the effective memory capacity and throughput of a memory constrained LPAR resulting in a 65% increase in application throughput
3. Enabling consolidation of more LPARs onto a system resulting in a 60% increase in overall system throughput