Vance P. Morrison

Applying control theory in the real world: experience with building a controller for the .NET thread pool

There has been considerable interest in using control theory to build web servers, database managers, and other systems. We claim that the potential value of using control theory cannot be realized in practice without a methodology that addresses controller design, testing, and tuning. Based on our experience with building a controller for the .NET thread pool, we develop a methodology that: (a) designs for extensibility to integrate diverse control techniques, (b) scales the test infrastructure to enable running a large number of test cases, (c) constructs test cases for which the ideal controller performance is known a priori so that the outcomes of test cases can be readily assessed, and (d) tunes controller parameters to achieve good results for multiple performance metrics. We conclude by discussing how our methodology can be extended, especially to designing controllers for distributed systems.