TECfan: Coordinating Thermoelectric Cooler, Fan, and DVFS for CMP Energy Optimization
Wenli Zheng, Kai Ma, Xiaorui Wang · 2016
The cooling needs of modern processors are dominantly provided by cooling fans, which can only offer global cooling capability. Even for cooling down one single hot unit (i.e., local hot spot), the fan needs to run at a high speed level, which consumes a lot of cooling power. Fortunately, emerging technologies, such as thermoelectric cooler (TEC), offer effective local cooling, which can be integrated with the fan to improve the overall cooling efficiency. However, relying on only TEC and fan may not optimize the total energy consumption of a chip multiprocessor (CMP), because the CMP core power states impact both computing and cooling power consumption. Therefore, for optimizing CMP energy, it is necessary to intelligently manage the processor power states and coordinate it with the cooling system. In this paper, we propose TECfan, a hierarchical runtime optimization framework that integrates TEC, fan, and DVFS for the overall energy efficiency of CMP. TECfan coordinates TEC and fan for efficient cooling, and also exploits DVFS to adapt the computing power consumption and execution time. Specifically, we first formulate CMP energy optimization with temperature constraint as a nonlinear optimization problem. Since there are no known polynomial-time algorithms for such a problem, solving it online is prohibitive. Hence, a novel heuristic algorithm is designed to solve it with acceptable time overheads. Our experiment results show that TECfan leads to 29% less energy consumption for medium workload compared to a state-of-the-art solution and 27%less overall compared to fan-based cooling.