Partition Load Manager for AIX®

The Partition Load Manager provides processor and memory resource management and monitoring across logical partitions within a single managed system that uses POWER5 technology.

Partition Load Manager allows you to more effectively use resources by allowing you to set thresholds for designated resources. When a threshold is exceeded, Partition Load Manager can try to assign resources to that logical partition by using resources assigned to other logical partitions that are not being used.

Partition Load Manager is available as part of the Advanced POWER® Virtualization feature.

When the Partition Load Manager resource manager starts, it registers several events on every required logical partition's node. The following events are registered individually on all of the managed logical partitions nodes:

• Memory-page-steal high thresholds
• Memory-usage high thresholds and low thresholds
• Processor-load-average high thresholds and low thresholds

The Partition Load Manager resource manager tracks these threshold values. Every time a threshold is exceeded, Partition Load Manager receives a Resource Monitoring and Control (RMC) event. When a high threshold is exceeded, the node needs more resources. Alternately, when a low threshold is crossed, the node has more resources available than it is currently using.

When a node requests additional resources, Partition Load Manager determines whether the node can accept additional resources. If the node can accept additional resources, Partition Load Manager conducts a search for available resources. Such additional resources can be found in the following places:

• The free pool, which is the list of currently unused resources maintained by Partition Load Manager. These resources are reallocated freely.
• Nodes that have indicated through events that they can release resources. These resources are removed from the node that does not require them and reallocated to the node that is requesting additional resources.
• Taken away from a node that has a lesser need for the resource, or a lower priority, than the node requesting the resource. These resources are removed from the node that has lower priority and reallocated to the node that is requesting additional resources.

Determining which node is more or less deserving of resources is primarily done by taking into account certain values defined in a policy file. This policy file details partitions, their entitlements, their thresholds, and organizes the partitions into groups. Every node, but not every logical partition, managed by Partition Load Manager must be defined in the policy file, along with several associated attribute values. Some of the attributes that are associated with the node are the maximum, minimum, and guaranteed resource values, variable share values, and so on. Partition Load Manager takes these attributes into account when a decision is made as to whether a resource is reallocated from one logical partition to another.

For example, a machine is likely to lose its resource to a node with a higher variable shares attribute value if that machine has a lesser variable shares attribute value and currently has more resource than the guaranteed resource value given in the policy file.