Fault Probability from Program Transition Diagram

, the estimate of a linear approximation supported by a rough measurement of the value of "a" for the load in question may be far more useful than having no model at all. Acknowledgments. Akira Sekino developed a hierarchical strategy for system modeling which exposed the usefulness of a model of the mean headway between missing pages [15]. Professor F.J. Corbat6 suggested that a linear model would be remarkably easy to manipulate, and almost inevitably a satisfactory approximation at some level. Robert M. Frankston helped develop the use of the linear model as a device for estimating load independent core memory use charges. Akira Sekino helped investigate the linear model as a basis for estimating sharing among parallel processes using the same virtual memory. Michael D. Schroeder provided hardware measurements of the Honeywell 645 associative memory, and Steven H. Webber invented and installed meters for measurement of the Multics virtual memory. References 1. Mattson, R.L., et al. Evaluation techniques for storage hierarchies. Experience using a time-shared multi-programming system with dynamic address relocation hardware. An algorithm is given for calculating page fault probability in a virtual memory system operating under demand paging with various memory sizes and replacement rules. A first order Markov model of program behavior is assumed, and a representation of the system based on memory states, control states, and memory substates is presented. The algorithm is general in the sense that the page fault probabilities can be calculated for nonpredictive replacement rules applied to any program represented by a one-step Markov chain. A detailed example is given to illustrate the algorithm for Random and Least Recently Used (LRU) replacement rules.