A novel CPU P-State driver for better thermal control with improved power/performance trade-off

Abstract

Power consumption and thermal emergencies in multi-core processors are now a major bottleneck due to increased heat dissipation caused by running intensive programs on densely integrated systems. High temperatures lead to unreliable and short lifespan of electronic devices. Currently, mechanisms are already in place so that whenever CPU reaches a cut-off temperature, the BIOS increases fan speed and conducts thermal throttling (adjusts the clock duty cycle and/or reduces the operating frequency/voltage). The problem of thermal control is exacerbated with the new Intel turbo boost, which opportunistically raises frequency leading to temperature spikes. Thus, there is increased need to control temperature at a set point via dynamic voltage and frequency scaling. Fortunately, modern CPU's provide P- States to operate it at various voltage-frequency pairs. P-States control temperature with the minimum loss in performance with the help of Proportional, Integral and Derivative (PID) based control. We implemented a Thermal head room based P-state driver (THBD) to reduce violations beyond target temperature. The THBD algorithm increases P-state only when there is enough thermal headroom, thus maintaining a steady temperature below the cut-off temperature, which could improve reduction in peak temperature and energy consumption by 1-4°C and 0.1-1.5 KJoules respectively with 0-7% increase in run-time penalty when evaluated with SPEC 2006 benchmark suite against PID based control.