Beyond Address Spaces - Flexibility, Performance, Protection, and Resource Management in the Type-Safe JX Operating System

Early type-safe operating systems were hampered by poor performance. Contrary to these experiences we show that an operating system that is founded on an object-oriented, type-safe intermediate code can compete with MMUbased microkernels concerning performance while widening the realm of possibilities. Moving from hardware-based protection to softwarebased protection offers new options for operating system quality, flexibility, and versatility that are superior to traditional process models based on MMU protection. However, using a type-safe language—such as Java—alone, is not sufficient to achieve an improvement. While other Java operating systems adopted a traditional process concept, JX implements fine-grained protection boundaries. The JX System architecture consists of a set of Java components executing on the JX core that is responsible for system initialization, CPU context switching and low-level domain management. The Java code is organized in components which are loaded into domains, verified, and translated to native