Shared Processor Partitions - IBM p5 590 System Handbook

a virtual Ethernet adapter and virtual SCSI server. Virtual Ethernet and virtual
SCSI are briefly explained in 3.3, "Virtual Ethernet" on page 65 and 3.6, "Virtual
SCSI" on page 81. Micro-Partitioning requires the Advanced POWER
Virtualization capabilities.

3.2.1 Shared processor partitions

The virtualization of processors enables the creation of a partitioning model
which is fundamentally different from the POWER4 systems where whole
processors are assigned to partitions and are owned by them. In the new model,
physical processors are abstracted into virtual processors that are then assigned
to partitions, but the underlying physical processors are shared by these
partitions.
Virtual processor abstraction is implemented in the hardware and firmware. From
an operating system perspective, a virtual processor is indistinguishable from a
physical processor. The key benefit of implementing partitioning in the hardware
is to allow an operating system to run on POWER5 technology with little or no
changes. Optionally, for optimal performance, the operating system can be
enhanced to exploit shared processor pools more in-depth. For instance, by
voluntarily relinquishing CPU cycles to the hardware when they are not needed.
AIX 5L Version 5.3 is the first version of AIX 5L that includes such
enhancements.
Micro-Partitioning allows for multiple partitions to share one physical processor.
Partitions using Micro-Partitioning technology are referred to as shared
processor partitions.
A partition may be defined with a processor capacity as small as 10 processor
units. This represents 1/10 of a physical processor. Each processor can be
shared by up to 10 shared processor partitions. The shared processor partitions
are dispatched and time-sliced on the physical processors under control of the
POWER Hypervisor.
Figure 3-1 on page 60 shows the POWER5 partitioning concept:
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Chapter 3. POWER5 virtualization capabilities