Thermal Aware Task Scheduling for Enhanced Cyber-Physical Systems Sustainability

Cyber-Physical Systems (CPS) are increasingly used in a variety of transportation, healthcare, electricity grid, and other applications. Thermal stress is often a major concern for processors embedded in such systems. High operating temperatures can dramatically shorten processor life. This, in turn, can require provisioning of significant amounts of additional computational hardware to withstand more frequent failures, with obvious implications for sustainability. This paper describes a novel approach to reduce thermally-induced damage in CPS processors by targeting Dynamic Voltage and Frequency Scaling (DVFS) to high-activity task phases. That is, by preferentially slowing down high-activity task phases, significant additional savings in energy and thermal stress can be attained for a given amount of computational slowdown; this approach is shown to be superior to conventional methods that use DVFS without regard to activity levels. Also, our proposed task reassignment across cores is driven by estimates of current core reliability, which is superior to the usual approach of simply using either current temperature or temperature history. Our approach leads to a significant reliability improvement (around 20 percent) over baseline DVFS techniques.