Resource contention is a conflict over access to a shared resource. Oversubscription can lead to contention, if not properly managed and monitored. Each of the primary four resources (CPU, memory, network, and disk) can experience contention.
CPU virtualization emphasizes performance and will run directly on the available processors when possible. Whenever possible, the underlying physical resources are used. The virtualization layer runs instructions only when needed to make sure that the virtual machines continue running as if directly accessing hardware on a physical server. A virtual machine can be configured with up to 64 virtual CPUs (vCPUs) as of vSphere 5.5. Keep in mind that a virtual machine cannot have more vCPUs than logical CPUs available on the ESXi host. The VMkernel includes a CPU scheduler that dynamically schedules vCPUs on the ESXi host's physical processor.
The CPU scheduler can use each logical processor independently to...