A Unifying Approach to Scheduling This paper presents a scheme for classifying scheduling algorithms based on an abstract model of a scheduling system which formalizes the notion of priority. Various classes of scheduling algorithms are defined and related to existing algorithms. A criterion for the implementation efficiency of an algorithm is developed and results in the definition of time-invariant algorithms, which include most of the commonly implemented ones. For time-invariant algorithms, the dependence of processing rates on priorities is derived. The abstract model provides a framework for implementing flexible schedulers in real operating systems. The policy-driven scheduler of Bernstein and Sharp is discussed as an example of such an implementation CACM July, 1977 Ruschitzka, M. Fabry, R. S. scheduling algorithms, scheduling models, priority, operating systems,processor sharing, implementation efficiency 4.31 4.32 4.34 4.35 8.1 CA770702 JB December 28, 1977 12:32 PM 2950 4 2950 3072 4 2950 2219 5 2950 2950 5 2950 2950 5 2950 2950 5 2950