DNS performance on Windows

Just to remember: I've got experience with heavy loaded domain controller with queries rate above 40k per second (yes, 40 thousand per second). The main problem on this virtual domain controller it was high cpu0 utilization and low load on other cpu. As I can remember - it was VMWare vm with 16 cores (virtual cores on operating system). What should be done in this case to improve performance? Upgrade of virtual hardware and network subsystem.