Real-time multiprocessor systems: performability evaluation

This paper deals with real-time systems required to provide not just timeliness of the computations performed but their correctness as well. Obviously, to improve figures of these two characteristics either cost must be raised or performance decreased. Here we propose a performability model which allows to distinguish among various possible trade-offs of such characteristics, and through which a quantitative evaluation of alternative system organisations and their comparison can be easily performed. Our performability model is based on a simple additive formulation of the concept of value in real time systems, which permits to derive the optimal schedule for a given system organisation. The numerical evaluation of a system organisation taken as example is performed for different load sets as well as a sensitivity analysis with respect to the most relevant parameters.