Techniques for the Design of Java Operating Systems

Godmar Back, Patrick Tullmann, Leigh Stoller, Wilson C. Hsieh, Jay Lepreau

April 2000

The Flux Research Group
Department of Computer Science
University of Utah
50 S. Central Campus Drive Rm. 3190
Salt Lake City, Utah 84112-9205


Language-based extensible systems, such as Java Virtual Machines and SPIN, use type safety to provide memory safety in a single address space. By using software to provide safety, they can support more efficient IPC. Memory safety alone, however, is not sufficient to protect different applications from each other. Such systems need to support a process model that enables the control and management of computational resources. In particular, language-based extensible systems should support resource control mechanisms analogous to those in standard operating systems. They need to support the separation of processes and limit their use of resources, but still support safe and efficient IPC.

We demonstrate how this challenge is being addressed in several Java-based systems. First, we lay out the design choices when implementing a process model in Java. Second, we compare the solutions that have been explored in several projects: Alta, K0, and the J-Kernel. Alta closely models the Fluke operating system; K0 is similar to a traditional monolithic kernel; and the J-Kernel resembles a microkernel-based system. We compare how these systems support resource control, and explore the tradeoffs between the various designs.

Full paper, to appear in Proceedings of the 2000 USENIX Annual Technical Conference, June 2000: