This chapter briefly covered virtualization and hypervisors to provide a background for understanding the JRockit Virtual Edition product family. Virtualization is the practice of running software on emulated, virtualized, hardware, and may potentially increase the resource utilization of a machine park. Virtualization also typically comes with some overhead because of the hardware emulation. A virtualized piece of software, for example an operating system, is called a guest. The two most important types of virtualization are full virtualization, where the guest does not know it is virtualized and can run unmodified in the virtualized environment, and paravirtualization that requires the guest to use a communication layer with the underlying system.

The piece of code making it possible to run multiple guests on a single piece of hardware is called a hypervisor. Except for "faking" the hardware to the guest and handling context switching between guests, it can help provide services...