Specifications

Chapter 3. Virtualization 87
Draft Document for Review May 12, 2014 12:46 pm 5102ch03.fm
When defining a shared processor partition, several options must be defined:
򐂰 The minimum, desired, and maximum processing units
Processing units are defined as processing power, or the fraction of time that the partition
is dispatched on physical processors. Processing units define the capacity entitlement of
the partition.
򐂰 The shared processor pool
Select one from the list with the names of each configured shared processor pool. This list
also displays, in parentheses, the pool ID of each configured shared processor pool. If the
name of the desired shared processor pool is not available here, you must first configure
the shared processor pool by using the shared processor pool Management window.
Shared processor partitions use the default shared processor pool, called DefaultPool by
default. See 3.4.3, “Multiple shared processor pools” on page 89, for details about multiple
shared processor pools.
򐂰 Whether the partition will be able to access extra processing power to “fill up” its virtual
processors above its capacity entitlement (selecting either to cap or uncap your partition).
If spare processing power is available in the shared processor pool or other partitions are
not using their entitlement, an uncapped partition can use additional processing units if its
entitlement is not enough to satisfy its application processing demand.
򐂰 The weight (preference) in the case of an uncapped partition.
򐂰 The minimum, desired, and maximum number of virtual processors.
The POWER Hypervisor calculates partition processing power based on minimum, desired,
and maximum values, processing mode, and is also based on requirements of other active
partitions. The actual entitlement is never smaller than the processing unit’s desired value, but
can exceed that value in the case of an uncapped partition and up to the number of virtual
processors allocated.
On the POWER8 processors, a partition can be defined with a processor capacity as small as
0.05 processing units. This number represents 0.05 of a physical core. Each physical core
can be shared by up to 20 shared processor partitions, and the partition’s entitlement can be
incremented fractionally by as little as 0.01 of the processor. The shared processor partitions
are dispatched and time-sliced on the physical processors under control of the POWER
Hypervisor. The shared processor partitions are created and managed by the HMC.
The Power S822 supports up to 20 cores in a single system, and these maximum numbers:
򐂰 20 dedicated partitions
򐂰 400 micropartitions (maximum 20 micropartitions per physical active core)
An important point is that the maximum amounts are supported by the hardware, but the
practical limits depend on application workload demands.
Consider the following additional information about virtual processors:
򐂰 A virtual processor can be running (dispatched) either on a physical core or as standby
waiting for a physical core to became available.
򐂰 Virtual processors do not introduce any additional abstraction level. They are only a
dispatch entity. When running on a physical processor, virtual processors run at the same
speed as the physical processor.
򐂰 Each partition’s profile defines CPU entitlement that determines how much processing
power any given partition should receive. The total sum of CPU entitlement of all partitions
cannot exceed the number of available physical processors in a shared processor pool.