Using Multiple Input, Multiple Output Formal Control to Maximize Resource Efficiency in Architectures

As processors seek more resource efficiency, they increasingly need to target multiple goals at the same time, such as a level of performance, power consumption, and average utilization. Robust control solutions cannot come from heuristic-based controllers or even from formal approaches that combine multiple single-parameter controllers. Such controllers may end-up working against each other. What is needed is control-theoretical MIMO (multiple input, multiple output) controllers, which actuate on multiple inputs and control multiple outputs in a coordinated manner. In this paper, we use MIMO control-theory techniques to develop controllers to dynamically tune architectural parameters in processors. To our knowledge, this is the first work in this area. We discuss three ways in which a MIMO controller can be used. We develop an example of MIMO controller and show that it is substantially more effective than controllers based on heuristics or built by combining single-parameter formal controllers. The general approach discussed here is likely to be increasingly relevant as future processors become more resource-constrained and adaptive.