Widening the Schedulability Hierarchical Scheduling Systems

This paper presents a compositional approach for schedulability analysis of hierarchical systems, which enables to prove more systems schedulable by having richer and more detailed scheduling models. We use a lightweight method (statistical model checking) for design exploration, easily assuring high confidence in the correctness of the model. A satisfactory design can be proved schedulable using the computation costly method (symbolic model checking). In order to analyze a hierarchical scheduling system compositionally, we introduce the notion of a stochastic supplier modeling the supply of resources in each component. We specifically investigate two different techniques to widen the set of provably schedulable systems: 1) a new supplier model; 2) restricting the potential task offsets. We also provide a way to estimate the minimum resource supply (budget) that a component is required to provide.