New On-Line Preemptive Scheduling Policies for Improving Real-Time Behavior

In real-time systems, schedulability is mandatory but other application-dependent performance criteria are most generally of interest. We first define the properties that a "good" real-time scheduling algorithm must possess. Then, we exhibit a class of easily-implementable policies that should be well suited to various applicative contexts because, in our experiments, these policies provide good trade-off between feasibility and the satisfaction of the application-dependent criteria. We propose a schedulability analysis generic for all policies within this class and evaluate other criteria by simulation. The study is illustrated in the framework of computer-controlled systems that are known to be sensitive to various delays induced by resource sharing.