Specifications

92 IBM Flex System p260 and p460 Planning and Implementation Guide
4.7 Active Memory Expansion
The optional Active Memory Expansion feature is a POWER7 technology that
allows the effective maximum memory capacity to be much larger than the true
physical memory. Applicable to AIX V6.1 or later, this innovative compression
and decompression of memory content using processor cycles allows memory
expansion of up to 100%.
This situation allows an AIX V6.1 or later partition to do more work with the same
physical amount of memory, or a server to run more partitions and do more work
with the same physical amount of memory.
Active Memory Expansion uses processor resources to compress and extract
memory contents. The trade-off of memory capacity for processor cycles can be
an excellent choice, but the degree of expansion varies, based on how
compressible the memory content is, and having adequate spare processor
capacity available for the compression and decompression. Tests in IBM
laboratories using sample workloads showed excellent results for many
workloads in terms of memory expansion per additional processor used. Other
test workloads had more modest results.
Clients have a great deal of control over Active Memory Expansion usage. Each
individual AIX partition can turn on or turn off Active Memory Expansion. Control
parameters set the amount of expansion wanted in each partition to help control
the amount of processor used by the Active Memory Expansion function. An IBM
Public License (IPL) is required for the specific partition that is turning on or off
memory expansion. After being turned on, monitoring capabilities in standard
AIX performance tools are available, such as lparstat, vmstat, topas,
and svmon.