Dynamic space-sharing in computer systems
Communications of the ACM
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This paper describes an operating system model that is based mainly on the DOS/VS supervisor but also reflects various design alternatives, providing a flexible tool for operating system design and tuning. The model is characterized by the subdivision of I/O activity into normal I/O, page I/O, and fetch I/O, corresponding to the different supervisor services involved. The model has been evaluated by analytical queuing methods in a set of APL functions that allow a fexible specification of the supervisor, the configuration, and the workload. Validation has been done by simulation and by benchmarking of a real system. The main features of this performance tool are described, and its capabilities are illustrated by performance results that show the impact of workload and various supervisor changes on system performance.