Exact analysis for basic single-rate cyclic executives

Abstract

The academic interest in cyclic executives for multitasking in hard real-time systems decreased significantly during the past decades. Moreover, cyclic executives are hardly addressed in contemporary text books, if at all. Cyclic executives are still in use, however, and there is therefore a need for analysis techniques for these executives. In this document, we consider two basic cyclic executives, i.e. a single-rate AFAP (as fast as possible) and a single-rate time-driven AFAP cyclic executive, scheduling a given sequence of independent hard real-time polling tasks in a single-processor system. We present exact analysis for both cyclic executives and discuss their relative strengths and weaknesses in terms of jitter, energy efficiency, and schedulability. Unlike existing approaches, which typically take periodic tasks as a starting point for cyclic executives and focus on schedulability of tasks, we take the schedulability of the system as a starting point, i.e. whether or not the system meets its deadlines. In particular, we do not assume periods and deadlines for tasks.