Quasi-Static Scheduling for Real-Time Systems with Hard and Soft Tasks
Proceedings of the conference on Design, automation and test in Europe - Volume 2
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In this paper we address the problem of static scheduling ofreal-time systems that include both hard and soft tasks. Weconsider that hard as well as soft tasks are periodic and thatthere exist data dependencies among tasks. In order to capture the relative importance of soft tasks and how the qualityof results is affected when missing a soft deadline, we useutility functions associated to soft tasks. Thus our objectiveis to find an execution order for tasks that maximizes thetotal utility and at the same time guarantees hard deadlines.We use the expected duration of tasks for evaluating utilityfunctions whereas we use the maximum duration of tasks forensuring that hard deadlines are always met. We present analgorithm for finding the optimal schedule and also differentheuristics that find near-optimal solutions at reasonable computational cost. The proposed algorithms are evaluated usinga large number of synthetic examples.