Control and Modeling Issues in Computer Operating Systems: Resource Management for Real-Rate Computer Applications

† This work was supported by in part by DARPA contracts/grants N66001-97-C-8522, N66001-97-C-8523, and F19628-95C-0193, NSF grants ECS-9988435 and CCR-9988440, and by Tektronix, Inc. and Intel Corporation. Abstract Commonplace computer applications on general-purpose computers increasingly are expected to meet “real-rate” requirements, processing or displaying data or images at an externally driven “rate”. We describe a feedbackcontrol-based resource manager design approach, allowing the computer system to allocate resources such as CPU and network bandwidth based on the measured “progress” of the applications. Progress is measured by separating a complex application into a number of simpler applications separated by buffers. The resource scheduler measures the buffer fill levels to determine whether the rates of data coming in and going out of each buffer are matched. Feedback controllers keep the buffer levels around a certain fill level. We have developed prototype systems in the Linux environment that demonstrate that (classical) feedback control can be used to match the real rates. However, more formal methods, such as those that can be developed by the control theory community, are needed to help with the analysis and design of such systems to make them commercially viable. This paper presents the computer system problems, results from the prototype designs showing feasibility, some preliminary modeling results, and demonstrations and discussions of which control modeling, analysis and design results and techniques appear to be relevant to this computer system problem, and why.