Technical information
Performance Best Practices for VMware vSphere 4.0
22 VMware, Inc.
Hardware-assisted MMU is supported for both AMD and Intel processors beginning with ESX 4.0 (AMD
processor support started with ESX 3.5 Update 1). On processors that support it, ESX 4.0 by default uses
hardware-assisted MMU virtualization for virtual machines running certain guest operating systems and uses
shadow page tables for others (see http://communities.vmware.com/docs/DOC-9882 for a detailed list). This
default behavior should work well for the majority of guest operating systems and workloads. If desired,
however, this can be changed, as described below.
The default behavior of ESX 4.0 regarding hardware-assisted virtualization can be changed using the vSphere
Client. To do so:
1 Select the virtual machine to be configured.
2Click Edit virtual machine settings, choose the Options tab, and select CPU/MMU Virtualization.
3 Select the desired radio button:
Automatic allows ESX to determine the best choice. This is the default;
http://communities.vmware.com/docs/DOC-9882 provides a detailed list of which VMM is chosen
for each combination of CPU and guest operating system.
Use software for instruction set and MMU virtualization disables both hardware-assisted CPU
virtualization (VT-x/AMD-V) and hardware-assisted MMU virtualization (EPT/RVI).
Use Intel® VT-x/AMD-V™ for instruction set virtualization and software for MMU virtualization
enables hardware-assisted CPU virtualization (VT-x/AMD-V) but disables hardware-assisted MMU
virtualization (EPT/RVI).
Use Intel® VT-x/AMD-V™ for instruction set virtualization and Intel® EPT/AMD RVI for MMU
virtualization enables both hardware-assisted CPU virtualization (VT-x/AMD-V) and
hardware-assisted MMU virtualization (EPT/RVI).
N
OTE When hardware-assisted MMU virtualization is enabled for a virtual machine we strongly recommend
you also—when possible—configure that virtual machine’s guest operating system and applications to make
use of large memory pages.
N
OTE Some combinations of CPU, guest operating system, and other variables (i.e, turning on Fault
Tolerance or using VMI) limit these options. If the setting you select is not available for your particular
combination, the setting will be ignored, and Automatic will be used.