CS 537 Notes, Section #21: Working Sets

Chapter 9, Sections 9.6 and 9.7 in Operating Systems Concepts.

Working Sets are a solution proposed by Peter Denning.

Peter J. Denning, The Working Set Model of Program Behavior, Communications of the ACM, 11 5, May 1968, pp. 323-333.

An informal definition is "the collection of pages that a process is working with, and which must thus be resident if the process is to avoid thrashing." The idea is to use the recent needs of a process to predict its future needs.

Working sets are not enough by themselves to make sure memory does not get overcommitted. We must also introduce the idea of a balance set:

As working sets change, corresponding changes will have to be made in the balance set.

Problem with the working set: must constantly be updating working set information.

This actual solution is an approximation algorithm known as WSClock.

Other questions about working sets and memory management in general:


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