Evaluation of a flexible task scheduling algorithm for distributed hard real-time systems

Most systems which are required to operate under severe real-time constraints assume that all tasks and their characteristics are known a priori. Scheduling of such tasks can be done statistically. Further, scheduling algorithms operating under such conditions are usually limited to multiprocessor configurations. The authors present a scheduling algorithm which works dynamically and on loosely coupled distributed systems for tasks with hard real-time constraints; i.e., the tasks must meet their deadlines. It uses a scheduling component local to every node and a distributed scheduling scheme which is specifically suited to hard real-time constraints and other timing considerations. Periodic tasks, nonperiodic tasks, scheduling overheads, communication overheads due to scheduling and preemption are all accounted for in the algorithm. Simulation studies are used to evaluate the performance of the algorithm.