IBM Power 750 - Page 143

Chapter 3. Virtualization 129
Capacity allocation above the entitled pool capacity (Level
1
)
The POWER Hypervisor initially manages the entitled pool capacity at the shared processor
pool level. This is where unused processor capacity within a shared processor pool is
harvested and then redistributed to uncapped micropartitions within the same shared
processor pool. This level of processor capacity management is sometimes referred to as
Level
0
capacity resolution.
At a higher level, the POWER Hypervisor harvests unused processor capacity from the
multiple shared processor pools that do not consume all of their entitled pool capacity. If a
particular shared processor pool is heavily loaded and several of the uncapped
micropartitions within it require additional processor capacity (above the entitled pool
capacity), then the POWER Hypervisor redistributes some of the extra capacity to the
uncapped micropartitions. This level of processor capacity management is sometimes
referred to as Level
1
capacity resolution.
To redistribute unused processor capacity to uncapped micropartitions in multiple shared
processor pools above the entitled pool capacity, the POWER Hypervisor uses a higher level
of redistribution, Level
1
.
Where there is unused processor capacity in under-utilized shared processor pools,
the micropartitions within the shared processor pools cede the capacity to the
POWER Hypervisor.
In busy shared processor pools, where the micropartitions have used all of the entitled pool
capacity, the POWER Hypervisor allocates additional cycles to micropartitions, in which
all of
the following statements are true:
򐂰 The maximum pool capacity of the shared processor pool hosting the micropartition
is not met.
򐂰 The micropartition is uncapped.
򐂰 The micropartition has enough virtual-processors to take advantage of the
additional capacity.
Under these circumstances, the POWER Hypervisor allocates additional processor capacity
to micropartitions on the basis of their uncapped weights independent of the shared
processor pool hosting the micropartitions. This can be referred to as Level
1
capacity
resolution. Consequently, when allocating additional processor capacity in excess of the
entitled pool capacity of the shared processor pools, the POWER Hypervisor takes the
uncapped weights of all micropartitions in the system into account, regardless of the multiple
shared processor pool structure.
Dynamic adjustment of maximum pool capacity
The maximum pool capacity of a shared processor pool, other than the default shared
processor pool
0
, can be adjusted dynamically from the managed console, using either the
graphical interface or the command-line interface (CLI).
Level
1
capacity resolution: When allocating additional processor capacity in excess of
the entitled pool capacity of the shared processor pool, the POWER Hypervisor takes the
uncapped weights of
all micropartitions in the system into account, regardless of the
multiple shared processor pool structure
.