LDoms are most efficient when they are allocated whole CPU cores. On the SPARC T4 and T5 servers, each CPU core has 8 threads. If multiple ldoms share a core:

• The per-core cache may be thrashed by the different workloads, causing unpredictable performance
• The automatic single-thread optimization feature on the CPU may work correctly, potentially halving single-thread performance

I would only ever use partial-core allocations on a "play" server where there is a need for more guest ldoms than there are CPU cores.

One use case for limiting the CPU usage is to reduce Oracle license costs through hard partitioning. Note that there are specific instructions for configuring ldoms to comply with Oracle's hard partitioning rules.

Alternatives:

• Hard partitioning can also be achieved by configuring zones to comply with Oracle's hard partitioning rules.