A time invariant working set model for independent reference

Under the Independent Reference Model (IRM) of program behavior, we study properties of the C space-time products as defined by Prieve and Fabry [21] for variable memory management algorithms. In particular, we look at the behavior of Denning's Working Set [11] and VMIN [21] algorithms. From the observed properties of these algorithms, we derive an algorithm which either keeps a page always in memory, or does not keep it at all. We show the online optimality of this algorithm under the assumption that the access probabilities are known a priori. Further, we propose a practical version of this algorithm for database and disk buffer management. By using our algorithm, we obtained space-time product improvements up to 41% over the Working Set algorithm.