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Increasing Fixed-Priority Schedulability using Non-Periodic Load Shapers
Ref: CISTER-TR-170506       Publication Date: 27 to 30, Jun, 2017

Abstract:
Many real-time systems use fixed-priority scheduling (FPS) for three main reasons: (i) it is easy to understand, configure and analyze, (ii) it has low runtime overhead, and (iii) it is widely implemented in operating systems. Moreover, it is enforced by some standards such as Autosar for safety-critical real-time applications since it avoids unbounded delays in the case of overload in the system. However, FPS is not optimal since it may prioritize the execution of a high-priority task over a task with an urgent deadline.
In this work, we introduce load-shaping (LS); a technique that shapes the workload of tasks to limit their impact on the system's schedulability while improving their safety. LS is implemented using a reservation server for each task. Each server has a budget that replenishes with a given pattern, which might not necessarily be periodic. In this work, we discuss the open problems regarding parameter assignment for load-shaping techniques.

Mitra Nasri

,

Geoffrey Nelissen

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