Generalizing Response-Time Analysis

In real-time theory, basically two approaches for the computation of response-times exist. One of them is the busy window method, the other is the real-time calculus, an extension of the network calculus. While both can be used to compute the bounds of response-times, they have different properties that make them suitable for different system architectures. The busy window approach on the one hand is able to obtain tight bounds for scheduling policies like round-robin. It is also capable of considering offsets, therefore delivering better results in the relevant cases. Hierarchical scheduling on the other hand can be better accounted for by the real-time calculus, where this is an inherent feature of the underlying concept. The approach we present in this paper takes the theory of hierarchy from the real-time calculus and uses it to generalize the response-time analysis. This is implemented as an extension of the busy window method, which enables it to analyze scheduling hierarchies of an arbitrary depth.