User-defined schedulers for real-time concurrent objects

Scheduling concerns the allocation of processors to processes, and is traditionally associated with low-level tasks in operating systems and embedded devices. However, modern software applications with soft real-time requirements need to control application-level performance. High-level scheduling control at the application level may complement general purpose OS level scheduling to fine-tune performance of a specific application, by allowing the application to adapt to changes in client traffic on the one hand and to low-level scheduling on the other hand. This paper presents an approach to express and analyze application-specific scheduling decisions during the software design stage. For this purpose, we integrate support for application-level scheduling control in a high-level object-oriented modeling language, Real-Time ABS, in which executable specifications of method calls are given deadlines and real-time computational constraints. In Real-Time ABS, flexible application-specific schedulers may be specified by the user, i.e., developer, at the abstraction level of the high-level modeling language itself and associated with concurrent objects at creation time. Tool support for Real-Time ABS is based on an abstract interpreter that supports simulations and measurements of systems at the design stage.