10. EDF in Real-Time Calculus

Response time analysis (RTA) is one of the key problems in real-time system design. This chapter proposes new RTA methods for EDF scheduling, with general system models where workload and resource availability are represented by request/demand bound functions and supply bound functions. The main idea is to derive response time upper bounds by lower-bounding the slack times. We first present a simple over-approximate RTA method, which lower bounds the slack time by measuring the “horizontal distance” between the demand bound function and the supply bound function. Then we present an exact RTA method based on the above idea but eliminating the pessimism in the first analysis. This new exact RTA method not only allows to precisely analyze more general system models than existing EDF RTA techniques, but also significantly improves analysis efficiency. Experiments are conducted to show efficiency improvement of our new RTA technique, and tradeoffs between the analysis precision and efficiency of the two proposed methods are discussed. We also illustrate the application of the proposed RTA techniques to Real-Time Calculus for the analysis of components with EDF scheduling in a distributed computing environment.