Active Memory Deduplication - IBM Power 750 Technical Overview And Introduction

3.4.7 Active Memory Deduplication

In a virtualized environment, the systems might have a considerable amount of
duplicated information stored on RAM after each partition has its own operating system,
and some of them might even share the same kind of applications. On heavily loaded
systems, this behavior might lead to a shortage of the available memory resources, forcing
paging by the Active Memory Sharing partition operating systems, the Active Memory
Deduplication pool, or both, which might decrease overall system performance.
Figure 3-13 shows the standard behavior of a system without Active Memory Deduplication
enabled on its Active Memory Sharing (shown as AMS in the figure) shared memory pool.
Identical pages within the same or different LPARs each require their own unique physical
memory page, consuming space with repeated information.
KEY:
Figure 3-13 Active Memory Sharing shared memory pool without Active Memory Deduplication
enabled
Active Memory Deduplication allows the hypervisor to dynamically map identical partition
memory pages to a single physical memory page within a shared memory pool. This way
enables a better utilization of the Active Memory Sharing shared memory pool, increasing the
system's overall performance by avoiding paging. Deduplication can cause the hardware to
incur fewer cache misses, which also leads to improved performance.
LPAR1
Logical Memory
U
U U U U
U U
D D
Mappings
D D D D U
U U U U U
AMS shared memory pool
D Duplicate pages
U
Unique pages
LPAR2
Logical Memory Logical Memory
U
U U U U
U U U
D
Without
Active Memory
Deduplication
U U U U
U U U U
LPAR3
U U
U U
U
D
U U
U U
Chapter 3. Virtualization
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