The working set model for program behavior

Probably the most basic reason behind the absence of a general treatment of resource allocation in modern computer systems is an adequate model for program behavior. In this paper a new model is developed, the “working set model”, which enables us to decide which information is in use by a running program and which is not. Such knowledge is vital for dynamic management of paged memories. The working set of pages associated with a process, defined to be the collection of its most recently used pages, is a useful allocation concept. A proposal for an easy-to-implement allocation policy is set forth; this policy is unique, inasmuch as it blends into one decision function the heretofore independent activities of process-scheduling and memory-management.