Advanced POWER Virtualization on IBM System p5 - Previous ...

Characteristics of WLM, PLM, and shared processors
Each of the available resource management mechanisms has its own
characteristics that distinguishes it from the others.
WLM
WLM monitors and manages the use of CPUs, memory, and disk I/O rates within
a stand-alone AIX 5L system or partition. It can limit the use of these resources
by particular processes or groups of processes. WLM places each process in a
class (a class may hold more than one process). Each class is allocated a
number of shares. The ratio of the shares owned by a class to the sum of the
shares of all active classes gives the proportion of the resources that the class
will receive. The shares mechanism results in a self-adapting percentage.
In a virtualized environment, WLM is able to manage competing demands for
memory, dedicated, and virtual processors, and disk I/O within a single AIX 5L
instance.
In dedicated processor partitions, WLM can assign classes to specific CPUs
using processor resource sets.
WLM periodically evaluates resource usage. It makes the necessary adjustments
to usage targets at the end of each period by acting on the process priorities.
WLM can manage resource usage conflicts as soon as they occur and for as
long as they last.
Note:
► WLM only has visibility of resource usage within a partition. It has no
visibility of what is happening in other partitions and cannot modify the
priority of a partition relative to other partitions.
► WLM is provided as part of AIX 5L.
PLM
PLM manages memory, dedicated processor partitions, and shared processor
partitions.
PLM manages partitions. It has no knowledge of the importance of any workload
running in the partitions and therefore cannot readjust priority based on the
changes of workload types.
PLM makes resource allocation decisions based on a policy file defined by the
system administrator and will request the HMC to perform the appropriate
dynamic LPAR operation.
432 <strong>Advanced</strong> <strong>POWER</strong> <strong>Virtualization</strong> on IBM System p5