On the Impacts of Greedy Thermal Management in Mobile Devices

As mobile system-on-chips incorporate multicore processors with high power densities, high chip temperatures are becoming a rising concern in mobile processors. Modern smartphones are limited in their cooling capabilities and employ CPU throttling mechanisms to avoid thermal emergencies by sacrificing performance. Traditional throttling techniques aim at achieving maximum utilization of the available thermal headroom so as to minimize the performance penalty at a given time. This letter demonstrates that such greedy techniques lead to fast elevation of temperature on other system components and cause substantially suboptimal performance over increased durations of phone activity. Through experiments on a commercial smartphone, we characterize the impact of application duration on throttling-induced performance loss and propose quality-of-service (QoS) tuning as an effective way of providing the mobile system user with consistent performance levels over extended application durations. The proposed QoS-aware frequency capping technique achieves up to 56% improvement in performance sustainability.