A Survey of Parallel Hard-Real Time Scheduling on Task Models and Scheduling Approaches

The trend towards multi-core systems becomes increasinglyomnipresentandhasalreadyreachedhardreal-time systems. In the recent years more and more researchers tackle the problem of scheduling parallel tasks with real-time constraints. We present a discussion of these recent approaches to hard real-time scheduling tasks consisting of multiple threads. We identify categories in scheduling mechanisms and task systems and discuss their features, as well as the research already achieved in their ???elds. In the domain of task models we identi???ed the gang constrained task model, the order constrained task model and the unconstrained task model. These task models differ regardingtheamountandtypeofthreadexecutionconstraints, which can be expressed using the model. Regarding scheduling algorithms, we identi???ed transformation based and nontransformation based scheduling schemes. The former rely on off-line task transformation, whereas the latter doesn???t require any prior information about task structures. The presented classi???cations show, that applied scheduling algorithms mostly are not restricted to certain task models, but that they are applied quite independently.