抢占阈值调度的功耗优化

DVS(Dynamic Voltage Scaling)技术的应用使得任务执行时间延长进而使得处理器的静态功耗(由CMOS电路的泄露电流引起)迅速增加.延迟调度(Procrastination Scheduling)算法是近年提出用于减少静态功耗的有效方法,它通过推迟任务的正常执行来尽可能长时间地让处理器处于睡眠或关闭状态,从而避免过多的静态功耗泄露.文中针对可变电压处理器上运用抢占阈值调度策略的周期性任务集合,将节能调度和延迟调度结合起来,提出一种两阶段节能调度算法,先使用离线算法来计算每个任务的最优处理器执行速度,而后使用在线模拟调度算法来计算每个任务的延迟时间,从而动态判定处理器开启/关闭时刻.实例研究和仿真实验表明,作者的方法能够进一步降低抢占阈值任务调度算法的功耗.

Leakage-Aware Energy-Efficient Scheduling for Fixed-Priority Tasks with Preemption Thresholds

Dynamic Voltage Scaling(DVS),which adjusts the clock speed and supply voltage dynamically,is an effective technique in reducing the energy consumption of embedded real-time systems.However,the longer a job is executed,the more energy in the leakage current the device/processor consumes for the job.Procrastination scheduling,where task execution can be delayed to maximize the duration of idle intervals by keeping the processor in a sleep/shutdown state even if there are pending tasks within the timing constraints imposed by performance requirements,has been proposed to minimize leakage energy drain.This paper targets energy-efficient fixed-priority with preemption threshold scheduling for periodic real-time tasks on a uni-processor DVS system with non-negligible leakage power consumption.A two-phase algorithm is proposed.In the first phase,the execution speed,i.e.,the supply voltage of each task are determined by applying off-line algorithms,and in the second phase,the procrastination length of each task is derived by applying on-line simulated work-demand time analysis,and thus the time moment to turn on/off the system is determined on the fly.A series of simulation experiments was evaluated for the performance of our algorithms.The results show that the proposed algorithms can derive energy-efficient schedules.