Support for real-time computing within general purpose operating systems-supporting co-resident operating systems

Distributed multimedia applications are typical of a new class of workstation applications that require real-time communication and computation services to be effective. Unfortunately, there remains a wide gap between the development of real-time computing technology in the research community and the deployment of real-time solutions in commercial systems. We explore technology for allowing two operating systems, a general purpose operating system and a predictable real-time kernel, to co-exist on the same hardware. We discuss the problems of multiplexing shared devices and partitioning shared data structures to accommodate two operating systems, and present a CPU executive that allows the IBM Microkernel (a derivative of the Mach microkernel) with an OSF/1 server to co-exist with a simple real-time kernel we have built. We also extend the traditional theory of scheduling periodic tasks on a uniprocessor to accommodate the case where a real-time kernel is allocated only a fraction of the total CPU capacity.