Effectively Scheduling Hard and Soft Real-Time Tasks on Multiprocessors

Real-time applications may be comprised of both soft and hard tasks, the former being related to streaming-based or other non-critical services. For these applications one is interested in minimizing the response time of soft tasks, for which quality of service is at stake, while not jeopardizing hard deadlines. In this paper, we propose a framework for multiprocessor real-time systems, that can schedule hard and soft tasks with unconstrained deadlines according to two EDF-based configurations. Our solution relies on two special servers, which are responsible for providing temporal isolation and slack reclaiming. These strategies are combined so that the average response time of soft tasks are improved. Results are evaluated via extensive simulation, which indicates that: the available processing capacity can be effectively utilized; average response time of aperiodic tasks is significantly reduced and hard deadlines are preserved while soft deadline miss ratio is kept low.