Specifications

Chapter 4. Product information and technology 93
Figure 4-18 represents the percentage of processor used to compress memory
for two partitions with various profiles. The green curve corresponds to a partition
that has spare processing power capacity. The blue curve corresponds to a
partition constrained in processing power.
Figure 4-18 Processor usage versus memory expansion effectiveness
Both cases show a knee of the curve relationship for processor resources
required for memory expansion:
򐂰 Busy processor cores do not have resources to spare for expansion.
򐂰 The more memory expansion that is done, the more processor resources
are required.
The knee varies, depending on how compressible the memory contents are. This
situation demonstrates the need for a case by case study to determine whether
memory expansion can provide a positive return on investment (ROI). To help
you perform this study, a planning tool is included with AIX V6.1 Technology
Level 4 or later. You can use this planning tool to sample actual workloads and
estimate both how expandable the partition memory is and how much processor
resources are needed. Any Power System model runs the planning tool.
% CPU
utilization
for
expansion
Amount of memory expansion
1 = Plenty of spare
CPU resource available
2 = Constrained CPU
resource – already
running at significant
utilization
1
2
Very cost effective