Had and issue today with virtual machines running on an ESX host. the VM’s were exhibiting poor performance and relatively high CPU usage even when doing very little.

Problem was eventually traced to Intel-VT not being enabled in the ESX host BIOS, as soon as the ESX host had Intel-VT enabled in the BIOS performance increased and CPU usage on the VM’s dropped.

On HP server Intel-VT appears to be disabled by default.

The AMD equivalent of Intel-VT is called AMD-V, again make sure it is enabled in the BIOS.