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

As processors seek more resource efficiency, theyincreasingly need to target multiple goals at the same time, such as a level of performance, power consumption, and averageutilization. Robust control solutions cannot come fromheuristic-based controllers or even from formalapproaches 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 inputsand control multiple outputs in a coordinated manner. In this paper, we use MIMO control-theory techniquesto 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 MIMOcontroller can be used. We develop an example of MIMO controllerand show that it is substantiallymore effective than controllers based on heuristics or builtby combining single-parameter formal controllers. The generalapproach discussed here is likely to be increasingly relevantas future processors become more resource-constrained and adaptive.