多核系统中基于Global EDF 的在线节能实时调度算法

随着多核系统能耗问题日益突出,在满足时间约束条件下降低系统能耗成为多核实时节能调度研究中亟待解决的问题之一.现有研究成果基于事先已知实时任务属性的假设,而实际应用中,只有当任务到达之后才能够获得其属性.为此,针对一般任务模型,不基于任何先验知识提出一种多核系统中基于Global EDF在线节能硬实时任务调度算法,通过引入速度调节因子,利用松弛时间,结合动态功耗管理和动态电压/频率调节技术,降低多核系统中任务的执行速度,达到实时约束与能耗节余之间的合理折衷.所提出的算法仅在上下文切换和任务完成时进行动态电压/频率调节,计算复杂度小,易于在实时操作系统中实现.实验结果表明,该算法适用于不同类型的片上动态电压/频率调节技术,节能效果始终优于Global EDF算法,最多可节能15％～20％,最少可节能5％～10％.

Global EDF-Based On-Line Energy-Aware Real-Time Scheduling Algorithm in Multi-Core Systems

As the energy consumption of multi-core systems becomes increasingly prominent, meeting the time constraints while reducing as much as possible system energy consumption is still an urgent problem in real-time energy-aware scheduling in multi-core system. Most existing works have assumptions on priori information of real-time tasks, but in real applications the tasks’ property be received only when the tasks arrive. Therefore, based on the general task model with no priori to tasks’ properties, this paper proposes a global EDF-based on-line energy-aware scheduling algorithm for hard real-time tasks in multi-core system. The proposed algorithm can reduce the execution speed of task in multi-core system and reach a reasonable compromise between real-time constraints and energy savings, as it introduces a speed scale factor for utilizing the slack time and combines dynamic power management with dynamic voltage/frequency scaling techniques. The algorithm implementsdynamic voltage/frequency scaling only in each context switch time and task completion time, with the smaller computational complexity, and easier to be included in real-time operating system. Experimental results show that the algorithm can be well applied to different kinds of dynamic voltage/frequency scaling on chip, and compared with Global EDF algorithm, it gain more energy savings in all cases, which can improve energy savings about 15% to 20% at most and about 5% to 10% at least.