Yukta: Multilayer Resource Controllers to Maximize Efficiency

Since computers increasingly execute in constrained environments, they are being equipped with controllers for resource management. However, the operation of modern computer systems is structured in multiple layers, such as the hardware, OS, and networking layers—each with its own resources. Managing such a system scalably and portably requires that we have a controller in each layer, and that the different controllers coordinate their operation. In addition, such controllers should not rely on heuristics, but be based on formal control theory. This paper presents a new approach to build coordinated multilayer formal controllers for computers. The approach uses Structured Singular Value (SSV) controllers from Robust Control Theory. Such controllers are especially suited for multilayer computer system control. Indeed, SSV controllers can read signals from other controllers to coordinate multilayer operation. In addition, they allow designers to specify the discrete values allowed in each input, and the desired bounds on output value deviations. Finally, they accept uncertainty guardbands, which incorporate the effects of interference between the controllers. We call this approach Yukta. To assess its effectiveness, we prototype it in an 8-core big. LITTLE board. We build a two-layer SSV controller, and show that it is very effective. Yukta reduces the ExD and the execution time of a set of applications by an average of 50% and 38%, respectively, over advanced heuristic-based coordinated controllers.