Proactive run-time mitigation for time-critical applications using dynamic scenario methodology

Energy saving is important for both high-end processors and battery-powered devices. However, for time-critical application such as car auto-driving systems and multimedia streaming, saving energy by slowing down speed poses a threat to timing guarantee of the applications. The worst-case execution time (WCET) is a widespread solution to this problem, but its static execution time model is not sufficient anymore for highly dynamic hardware and applications nowadays. In this work, a fully proactive run-time mitigation methodology is proposed for energy saving while ensuring timing guarantee. This methodology introduces heterogeneous datapath options, a fast fine-grained knob which enables processors to switch between datapaths of different speed and energy levels with a switching time of only tens of clock cycles. In addition, a run-time controller using a dynamic scenario methodology is developed. This methodology incorporates execution time prediction and timing guarantee criteria calculation, so it can dynamically switch knobs for energy saving while rigorously still ensuring all timing guarantees. Simulation shows that the proposed methodology can mitigate a dynamic workload without any deadline misses, and at the same time energy can be saved.