Overloads in Compositional Embedded Real-Time Control Systems

Component-based design is important for the design of complex embedded software. By properly defining component interfaces, new components can be formed by composing existing components. A newly formed component may be further composed of other components. One of the key requirements for guaranteeing the compositionality of components in real-time systems is that the composite model must be consistent with, and indistinguishable from, the interface of a primitive component so that all real-time requirements are met. In addition to being used widely for schedulability analysis on different techniques such as earliest deadline first (EDF) and rate monotonic (RM), supply-demand functions have been applied to perform compositional schedulability analysis with periodic resource models. However, supply-demand function analysis for compositional schedules has only been done for hard real-time systems guarantees. This work analyzes overloads in embedded real-time control systems with soft deadlines and the analysis helps to build a compositional system that can tolerate delays. This paper also associates the schedulability analysis with a control application using a rapid prototype implementation.