IBM released a very interesting whitepaper about VMware technologies:
This paper discusses a performance optimization in the VMware ESX Server 2.5.3 and ESX Server 3.0 scheduler that can benefit Intel® processor-based IBM® NUMA-class servers with hyperthreading enabled. This paper describes the test environment and presents the results obtained with and without the performance optimization.
The information presented is based on our experience with setting up and running VMware ESX Server configurations in the IBM System x™ Performance Laboratory.
Read the it at source.