Hard real-time scheduling for the rate-group model

Typescript (photocopy).Many real-time systems built in the past based their scheduling on the cyclic executive model because it produces predictable schedules which facilitate exhaustive testing. The rate-monotonic algorithm has the advantage of a strong theoretical foundation and holds out the promise of reducing the need for exhaustive testing of the scheduling. Most approaches based on the rate-monotonic algorithm rely on many assumptions which differ from the characteristics of real applications. In real systems, applications may have several characteristics require more customized system design. In this work we examine how to exploit application characteristics and how to address specific application needs. We study the rate-group model, which combines features of the cyclic executive model and the rate-monotonic algorithm. This model turns out to have some advantages from the point of view of the applications programmer, and is particularly useful in the context of large critical systems designed by several groups of programmers, such as space and defense systems