Improved Fixed Priority discipline for Low-Overhead Real-Time Embedded Schedulers

R. Cayssials, E. Ferro and J. Orozco


(RealTime, Embedded Systems, Fixed Priority, Precedence Relations, Dual Priority Scheduling.)


Modern real time systems are widely used in more di verse and demanding areas each time. However, their temporal requirements are analysed under the real time theory just oriented to critical applications. Both Fixed Priority and Earliest Deadline First disciplines have been proposed as the most suitable scheduling algorithms for real time systems because of their tem poral properties. Fixed priority schemes have the dis advantage that processor utilisations equal to 100% is rarely attainable when hard real time requirements have to be guaranteed. By comparison, Earliest Dead line First scheduling are theoretically able to obtain a full processor utilisation, although in practice run-time overheads are increased that undermine this advantage [2]. In this paper, a low-overhead scheme is proposed to improve the real time performance of a fixed priority discipline. This scheme is oriented to be suitable for embedded applications in which resources are scarce and its utilisation has to be maximised.

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