JETC: Joint Energy Thermal and Cooling Management for Memory and CPU Subsystems in Servers

In this work we propose a joint energy, thermal and cooling management technique (JETC) that significantly re-duces per server cooling and memory energy costs. Our analysis shows that decoupling the optimization of cooling energy of CPU & memory and the optimization of mem-ory energy leads to suboptimal solutions due to thermal de-pendencies between CPU and memory and non-linearity in cooling energy. This motivates us to develop a holistic so-lution that integrates the energy, thermal and cooling man-agement to maximize energy savings with negligible per-formance hit. JETC considers thermal and power states of CPU & memory, thermal coupling between them and fan speed to arrive at energy efficient decisions. It has CPU and memory actuators to implement its decisions. The memory actuator reduces the energy of memory by performing cool-ing aware clustering of memory pages to a subset of mem-ory modules. The CPU actuator saves cooling energy by reducing the hot spots between and within the CPU sockets and minimizing the effects of thermal coupling. Our exper-imental results show that employing JETC results in 50.7% average energy reduction in cooling and memory subsys-tems with less than 0.3 % performance overhead. 1