Virtual scheduling for compositional real-time guarantees

In this paper, we extend the compositional scheduling framework to enable the integration of an existing (legacy) application as a component on a faster processor which needs to be shared with other components. After admission of this application into the framework, the integrated component still has to satisfy its tasks´ deadline constraints and it must execute jobs in the same order as it did previously on the dedicated processor, regardless of the actual supply of processor resources. We propose a method - called virtual scheduling - which establishes this by reconstructing an appropriate order of delivering events. Virtual scheduling is therefore independent of the component-level scheduling policy and it is transparent to a component, so that it is even applicable without making modifications to the code or specification of the application.