Dual Priority Scheduling: A Means of Providing Flexibility in Hard Real-time Systems.

In this paper, we present a new strategy for providing flexibility in hard real-time systems. This approach, based on dual priorities, retains the offline guarantees afforded to crucial tasks by fixed priority scheduling. Further, it provides an efficient method of responsively scheduling soft tasks and a means of providing online guarantees for tasks with firm deadlines. An effective O (n ) acceptance test is derived in the paper. Supported by the analysis, acceptance tests and mechanisms described, the dual priority approach provides a basis for combining the benefits of guaranteeing hard requirements with the flexibility inherent in the besteffort paradigm. 1. Introduction The requirement to support dynamic, adaptive and intelligent behaviour whilst also providing the 100% guarantees needed by crucial hard real-time services, has been identified as one of the key challenges presented by the next generation of real-time systems [8]. In this paper, we present a minimally dynamic sch..