Over provisioning vCPUs can cause your VM to run slow

I came across a nice article today explaining various inside outs of vCPUs in VMware ESXi. It talks starting from how vCPUs are formed and its relation with physical CPUs, how multi-threading effects no. of vCPUs, and more importantly how over provisioned vCPUs can cause your Virtual machine to run slow compared with virtual machines with single vCPU.

http://www.virtualinstruments.com/sanbestpractices/best-practices/avoiding-the-virtual-cpu-dilemma-overprovisioning-vcpu-to-pcpu-ratios/

I feel its worth reading..