Extending the Chorus Micro-Kernel to Support Continuous Media Applications

Currently, popular operating systems are unable to support the end-to-end real-time requirements of distributed continuous media. Furthermore, the integration of continuous media communications software into such systems poses significant challenges. This paper describes a design for distributed multimedia support in the Chorus micro-kernel operating system environment which provides the necessary soft real-time support while simultaneously running conventional applications. Our approach is to extend existing Chorus abstractions to include QoS configurability, connection oriented communications and real-time threads. The design uses the following key concepts: the notion of a flow to represent QoS controlled communication between two application threads, a close integration of communications and thread scheduling and the use of a split level scheduling architecture with kernel and user level threads. The paper shows how our design qualitatively improves performance over existing micro-kernel facilities by reducing the number of protection domain crossings and context switches incurred.