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Most research in free-storage management has centered around strategies that search a linked list and strategies that partition storage into predetermined sizes. Such algorithms are analyzed in terms of CPU efficiency and storage efficiency. The subject of this study is the free-storage management in the Virtual Machine/System Product (VM/SP) system control program. As a part of this study, simulations were done of established, and proposed, dynamic storage algorithms for the VM/SP operating system. Empirical evidence is given that simplifying statistical assumptions about the distribution of interarrival times and holding times has high predictive ability. Algorithms such as first-fit, modified first-fit, and best-fit are found to be CPU-inefficient. Buddy systems are found to be very fast but suffer from a high degree of internal fragmentation. A form of extended subpooling is shown to be as fast as buddy systems with improved storage efficiency. This algorithm was implemented for VM/SP, and then measured. Results for this algorithm are given for several production VM/SP systems.
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