Operating System Support for Virtual Machines

A virtual-machine monitor (VMM) is a useful technique for adding
functionality below existing operating system and application
software. One class of VMMs (called Type II VMMs) builds on the
abstractions provided by a host operating system. Type II VMMs are
elegant and convenient, but their performance is currently an order
of magnitude slower than that achieved when running outside a virtual
machine (a standalone system). This talk examines the reasons
for this large overhead for Type II VMMs. We find that a few simple
extensions to a host operating system can make it a much faster
platform for running a VMM. Taking advantage of these extensions
reduces virtualization overhead for a Type II VMM to 14-35% overhead,
even for workloads that exercise the virtual machine intensively.