Maestro: Autonomous QoS Management for Mobile Applications Under Thermal Constraints

Power densities of modern mobile system-on-a-chip designs can quickly exceed the thermal design limits during typical application use such as gaming or Web browsing. Resulting high temperatures lead to frequent thermal throttling and significant loss in quality-of-service (QoS) delivered to users. Thus, a joint consideration of thermal constraints and QoS requirements is essential to maximize the overall user experience. Prior techniques either rely on users to determine the best tradeoff point between QoS and temperature, or greedily utilize the thermal headroom to maximize performance, causing QoS to drop below user tolerable levels over extended durations of use. This paper introduces the MAESTRO framework to automatically manage QoS at runtime depending on application characteristics and thermal constraints. MAESTRO builds on the observation that increased temperatures can be tolerated for applications with bursty compute patterns due to idle periods between activities, while causing large QoS degradations for long-running applications with continuous computations. MAESTRO: 1) detects such continuous computations that are susceptible to throttling; 2) proactively finds a QoS level to balance user experience and temperature; and 3) performs closed-loop DVFS and thermally efficient thread mapping to meet the target QoS on a heterogeneous multicore CPU. Such application-adaptive control of QoS-temperature tradeoffs allows MAESTRO to sustain a target QoS level within a user tolerable range for longer durations without sacrificing the performance of latency-sensitive bursty computations. Evaluations on a real system prototype validates MAESTRO's ability to accurately detect potential throttlinginduced QoS degradations and demonstrates 41% to 6.7× longer durations of sustained QoS compared to state-of-the-art for a set of mobile applications.