The Real-Time Computing Laboratory, Web QoS Group

Control-Theory for Performance Guarantees Sponsor: NSF

Many modern applications, such as multimedia streaming, embedded real-time computing, reliable transaction processing, web hosting, and e-commerce require some form of performance guarantees. Two forms of performance guarantees have been investigated in prior literature; namely absolute and statistical. In this project, we investigate a different form we call convergence guarantees. These guarantees are softer than deterministic but offer more information on transient behavior than statistical.

In essence a convergence guarantee states that the system will converge to the desired specifications under certain conditions and within a specificed convergence envelope. Control theory is used as the underlying theoretic engine to provide convergence guarantees. The intuitive reason why performance of computing services can be modeled within a control-theoretic framework is because this performance depends on queueing delays at different computing resources (e.g., CPU, sockets, semaphores, network). Queues act as integrators of flows. Hence the computing system can be modeled by differential equations amenable to control-theoretic analysis.

Control systems have traditionally been employed in industry to manipulate the value of controlled system parameters. In particular, robust control and adaptive control theory deal with the problem of achieving a desired system performance in the absence of complete knowedge of controlled system dynamics. We are interested in applying elements of these theories in the Internet application domain to control the behavior of distributed performance-critical services in the absence of good system models and a priori information on load and resource usage patterns.

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For more information on please visit the feedback-control scheduling web page.

Selected Publications:

Contributions in Modeling and QoS-Control of Computing Systems using Control Theory:

• Tarek Abdelzaher, Kang G. Shin, Nina Bhatti, ``User-Level QoS-Adaptive Resource Management in Server End-Systems,'' IEEE Transactions on Computers, accepted for publication, 2003.

• Lui Sha, Xue Liu, Ying Lu, Tarek Abdelzaher, ``Queuing Model Based Network Server Performance Control,'' Real-Time Systems Symposium, Austin, TX, December 2002.

• Ying Lu, Gang Tao, and Tarek Abdelzaher, ``LDU Parametrized Discrete Time Multivariable MRAC and Application to a Web Cache System,'' IEEE Conference on Decision and Control, Las Vegas, Nevada, December 2002.

• Ronghua Zhang, Chenyang Lu, Tarek F. Abdelzaher, John A. Stankovic, ``ControlWare: A Middleware Architecture for Feedback Control of Software Performance,'' International Conference on Distributed Computing Systems, Vienna, Austria, July 2002.

• Ying Lu, Chanyang Lu, Tarek Abdelzaher, Gang Tao, ``An Adaptive Control Framework for QoS Guarantees and its Application to Differentiated Caching Services,'' IWQoS, Miami Beach, FL, May 2002.

• Tarek Abdelzaher, Kang G. Shin, Nina Bhatti, ``Performance Guarantees for Web Server End-Systems: A Control-Theoretical Approach,'' IEEE Transactions on Parallel and Distributed Systems , Vol. 13, No. 1, Jan 2002.

• John Stankovic, Tian He, Tarek Abdelzaher, Mike Marley, Gang Tao, Sang Son, ' ``Feedback Control Scheduling in Distributed Systems,'' IEEE Real-Time Systems Symposium, London, UK, December 2001.

• Chenyang Lu, Tarek Abdelzaher, Jack Stankovic, Sang Son, ``A Feedback Control Approach for Guaranteeing Relative Delays in Web Servers,'' IEEE Real-Time Technology and Applications Symposium, TaiPei, Taiwan, June 2001.

• Ying Lu, Avneesh Saxena, and Tarek F. Abdelzaher, ``Differentiated Caching Services; A Control-Theoretical Approach,'' International Conference on Distributed Computing Systems, Phoenix, Arizona, April 2001.

• Tarek F. Abdelzaher and Chenyang Lu, ``Modeling and Performance Control of Internet Servers,'' Invited Paper, 39th IEEE Conference on Decision and Control, Sydney, Australia, December 2000.

• Chenyang Lu, John A. Stankovic, Tarek F. Abdelzaher, Gang Tao, Sang H. Son and Michael Marley, ``Performance Specifications and Metrics for Adaptive Real-Time Systems,'' IEEE Real-Time Systems Symposium, Orlando, Florida, December 2000.

• Tarek F. Abdelzaher, ``An Automoated Profiling Subsystem for QoS-Aware Services,'' IEEE Real-Time Technology and Applications Symposium, Washington D.C., June 2000.

• Tarek F. Abdelzaher and Kang G. Shin, ``QoS Provisioning with qContracts in Web and Multimedia Servers,'' IEEE Real-Time Systems Symposium, Pheonix, Arizona, December 1999.

• Tarek F. Abdelzaher, Nina Bhatti, ``Adaptive Content Delivery for Web Server QoS,'' International Workshop on Quality of Service, London, UK, June 1999.

• Tarek F. Abdelzaher, Nina Bhatti, ``Web Content Adaptation to Improve Server Overload Behavior,'' International World Wide Web Conference, Toronto, Canada, May 1999.

• Tarek F. Abdelzaher, Kang G. Shin, ``End-host Architecture for QoS-Adaptive Communication,'' IEEE Real-Time Technology and Applications Symposium, Denver, Colorado, June 1998.

• Tarek F. Abdelzaher, S.A. Hammad, A.Z. Badr and M.A. Sheirah "Experimental Validation for Modeling and Identification of a Pilot Industrial Process" in Proc 3rd IASTED International Conference, Cairo, Egypt, December, 1994.

• M.A. Sheirah, Tarek F. Abdelzaher, "Embedded Real Time Systems," in proc. Symposium on New Horizons in Computers and Information Systems, Cairo, Jan 26-28, 1993.

• Tarek F. Abdelzaher, M.A. Sheirah, "Identification Algorithm for Multicapacity Systems with Dead Time," Proceedings of the Second IASTED International Conference, Alexandria, Egypt, May 5-7, 1992.

• Tarek F. Abdelzaher, M.A. Sheirah, "Generalized PID Tuning Method," Proceedings of the Second IASTED International Conference, Alexandria, Egypt, May 5-7, 1992.