Abstract
A program's working set is the collection of segments (or pages) recently referenced. This concept has led to efficient methods for measuring a program's intrinsic memory demand; it has assisted in undetstanding and in modeling program behavior; and it has been used as the basis of optimal multiprogrammed memory management. The total cost of a working set dispatcher is no larger than the total cost of other common dispatchers. This paper outlines the argument why it is unlikely that anyone will find a cheaper nonlookahead memory policy that delivers significantly better performance.