Task Merging for Dynamic Power Management of Cyclic Applications in Real-Time Multiprocessor Systems

In this paper we propose the method of task merging and idle period clustering for dynamic power management (DPM) in a real-time system with multiple processing elements. We show that with good task scheduling, the energy and delay overheads due to power mode switching can be reduced significantly, while the opportunity for the system to switch to low power modes can be further improved. New on-line and off-line task scheduling algorithms are proposed that minimize the number of idle time intervals under the deadline and precedence constraints. A simple DPM policy is then used to save the energy dissipation during the idle time intervals. Experimental results show that, comparing to the DPM schemes without proper task scheduling, the proposed method reduces the number of power mode switching by 56% in average.