LoCool: Fighting Hot Spots Locally for Improving System Energy Efficiency
LoCool: Fighting Hot Spots Locally for Improving System Energy Efficiency
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DOI：
10.1109/tcad.2019.2902355
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发表时间：
2020-04-01
影响因子：
2.9
通讯作者：
Coskun, Ayse K.
中科院分区：
文献类型：
--
作者：
Kaplan, Fulya;Said, Mostafa;Coskun, Ayse K.
升高的片内温度会显著降低处理器的性能、能效和寿命。芯片的冷却系统通常被设计为去除每单位面积产生的最坏情况的热量。然而，冷却需求在空间上和时间上跨芯片变化，因为热点以不同强度出现在不同位置上。因此，为芯片设计均匀的冷却系统可能是低效的。最近，混合冷却策略，如集成热电冷却器（TEC）与微通道液体冷却，已被探索的热点缓解。这种冷却系统的效率在很大程度上取决于每种冷却方法的操作点以及热点的位置和强度。为此，我们首先设计了一种紧凑的热建模方法，用于快速准确地设计和评估混合冷却系统。与COMSOL多物理场模拟相比，该模型在模拟时间上提供了高达四个数量级的加速，平均温度误差小于2.9摄氏度。利用我们的快速模型，我们开发了LoCool，这是一种混合冷却优化方法，它可以针对给定的芯片功率分布和温度约束共同确定最节能的冷却设置。LoCool根据各个热点以及背景热的冷却要求确定每个TEC的液体流速和输入电流。实验评估显示，在相同的热约束条件下，与设计均匀冷却系统相比，可节省高达40%的冷却能量。
Elevated on-chip temperatures significantly degrade performance, energy-efficiency, and lifetime of processors. The cooling system for a chip is typically designed to remove the worst-case heat generated per unit area. Cooling demand, however, spatially and temporally varies across a chip as hot spots occur on different locations with different intensities. Thus, designing a homogeneous cooling system for a chip can be inefficient. Recently, hybrid cooling strategies, such as integrating thermoelectric coolers (TECs) with microchannel liquid cooling, have been explored for hot spot mitigation. The efficiency of such a cooling system strongly depends on the operating point of each cooling method, as well as the locations and intensities of the hot spots. To this end, we first devise a compact thermal modeling method for the design and evaluation of hybrid cooling systems in a fast and accurate way. The proposed model provides up to four orders of magnitude speedup in simulation time compared to COMSOL multiphysics simulations with less than 2.9 degrees C average temperature error. Leveraging our fast model, we develop LoCool, a hybrid cooling optimization method, which jointly determines the most energy-efficient cooling settings for a given chip power distribution and temperature constraint. LoCool determines the liquid flow rate and the input current for each TEC depending on the cooling requirements for individual hot spots as well as for the background heat. Experimental evaluation shows up to 40% cooling energy savings compared to designing homogeneous cooling systems under the same thermal constraints.