IPA in the loop: Control design for throughput regulation in computer processors

A new technique for performance regulation in event-driven systems, recently proposed by the authors, consists of an adaptive-gain integral control. The gain is adjusted in the control loop by a real-time estimation of the derivative of the plant-function with respect to the control input. This estimation is carried out by Infinitesimal Perturbation Analysis (IPA). The main motivation comes from applications to throughput regulation in computer processors, where to-date, the testing of the proposed control technique has been assessed by simulation. The purpose of this paper is to report on its implementation on Intel's Haswell microprocessor, and compare its performance to that obtained from cycle-level, full system simulation environment. The intrinsic contribution of the paper to the Workshop on Discrete Event Systems is in describing the process of taking an IPA-based design and simulation to a concrete implementation, thereby providing a bridge between theory and applications.