Cool shapers: Shaping Real-Time Tasks for Improved Thermal Guarantees

Pratyush Kumar and Lothar Thiele.
Design Automation Conference 2011, June 5th-10th, 2011. San Diego, California, USA.
With increasing power densities, managing on-chip temperatures has become an important design challenge. We propose a novel approach to this problem with the use of shapers to dynamically and selectively insert idle times during the execution of hard real-time jobs on a single speed processor. For the class of leaky bucket shapers which have a light-weight implementation, we derive the shaper such that no job misses its real-time deadline and the peak temperature is optimally reduced. The analysis and design of such shapers allows for dynamically variable streams of jobs; for instance, periodic streams with jitter. We extend our results to consider non-zero power and timing overhead in transitioning to the idle mode. With experimental results, we demonstrate that the proposed approach provides a large improvement: on average 8K peak temperature reduction or 40% increase in utilization for a given peak temperature.