Event Stream Calculus for Schedulability Analysis
IFIP Advances in Information and Communication Technology
In the paper we will show the integration of the real-time calculus with event driven real-time analysis like the periodic or the sporadic task model. For the event-driven real-time analysis, flexible approximative analysis approaches where proposed to allow an efficient real-time analysis. We will provide an easy but powerful approximative description model for the real-time calculus. In contrary to the existing description model the degree of approximation is chooseable allowing a more
... e description. Motivation The module-based design processes makes it possible to handle the complexity in software and hardware design. Systems are built using a set of closed modules. These modules can be designed and developed separately. Modules have only designated interfaces and connections to other modules of their set. The purpose of modularization is to split the challenging job of designing the whole system into multiple smaller jobs. Another purpose is to allow the reuse of modules in different designs or use IP components of third-party vendors. Each module-based design concept needs a well defined interface-concept for connecting the different modules. For developing real-time systems a concept for analysing the system which can handle the real-time aspects of the different modules separately and allows to propagate the results through the system is required. One aspect of this concept is the timing description of events which are produced by one module to trigger the next following module. Another aspect is the remaining computation capacity for the next module left over by the previous module. Consider for example a network packet processor as shown in figure 1 . The single packages are processed by chains of tasks τ which can be located on different processing elements P. The processing elements P can be processors, dedicated hardware or the communication network. The events Θ triggering the different tasks are equal to the packages flowing through the network. Each processing unit P uses a fixed-priority scheduling and the tasks τ on each unit are sorted by their priority level. Each task τ has, as available capacity, the capacity S left over by the tasks τ with a higher priority located on the same processing unit. The purpose of this paper is to provide an efficient and flexible approach for the realtime analysis of such a modularized system. Necessary therefore is a powerful and sufficient event model for describing the different time interfaces for the different aspects.