VMware just released a new 21 page white paper entitled VMware vSphere 4: The CPU Scheduler in VMware ESX 4 that is all about how the mysterious CPU scheduler functions. This is a highly recommended read and the scheduler is one of the most important components of the hypervisor and therefore you should understand how it functions. The white paper details how the scheduler works, changes made to it in ESX 4, verifies the effectiveness of CPU resource controls including Shares/Reservations/Limits, compares different co-scheduling algorithms and evaluates the performance impact of CPU scheduler changes in ESX 4. Be sure and go check it out.