Thursday, January 1, 2009

VirtualBox Hardware Virtualization and Nested Paging

Recently discovered that I could enable nested paging for Virtualbox 2.1.
Nested paging is a new hardware virtualization extension on AMD K10 Barcelona/Phenom and Intel Core i7 Nehalem processors that allows processor to offload memory paging required by the guest OS that is traditionally done by the VM with shadow paging.
Since it is a new feature, it is not available in the configuration UI yet.
First, you will have to enable hardware virtualization (VT-x/AMD-V) in Settings -> Advanced. Then, nested paging can be enabled as described in the VirtualBox User Manual with the following command:
VBoxManage modifyvm   -nestedpaging on

The performance boost is quite noticeable.
The boot up time for my virtual Windows XP has drop from about 25 seconds to 18 seconds.
Super PI Mod has dropped from 39.159s to 36.016s
Various benchmarks on the net show performance boost up to 30%.
I'll run more benchmarks next time.
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