Energy Management Research And Application Of Power-Aware Real-Time Systems

CMOS technology is the basis of the modern computer systems. However, power consumption is facing an increasingly severe challenge along with the advancing of technology. Power aware computing has recently become popular not only for hand-held devices that have limited energy supply but also for large systems consisting of multiple processors, for example, complex satellite and surveillance systems, data warehouses, etc. The sharply increase of power consumption results in not only higher cost of chip encapsulation and cooling, but also the reduction of system stability because running chip on high temperature will missing chip efficiency.Dynamic voltage scaling is an effective low-power technique. There is a quadratic relationship between power consumption of system and supply voltage, a linear dependence between the frequency and supply voltage, resulting in a linear increase on the execution time of a task when the frequency is decreased. Therefore, when the supply voltage decreasing, the frequency gets a linear decrease and the execution time of a task gets a linear increase, the energy consumption of system gets a quadratic decrease. It is an effective method to decrease power dissipation by adjusting supply voltage when the task is executing. Dynamic voltage scaling method can be devised at different levels of system design, and at system level, dynamic voltage scaling method mainly selecting appropriate scheduling algorithm in scheduling modules and adjusting supply voltage.In real-time systems, dynamic voltage scaling mechanism must to consider some facets, including the deadline and periodicity of tasks in order to guarantee time requirement of real-time tasks. Dynamic voltage scaling mechanism also needs to combine wuith scheduling algorithms of real-time systems to reduce energy consumption of systems. In this paper,we concentrate on reducing energy consumption by using task scheduling algorithm on system level when these tasks have time restrictions in real-time systems. This paper addresses the conception of CMOS circuit at first, analyzes low-power principles of CMOS circuit and some questions about dynamic voltage scaling technique, then makes a comparison between single task low-power scheduling algorithms and multiple tasks low-power scheduling algorithms in real-time system. Finally this paper carries on the analysis to the scheduling questions based on dynamic voltage scaling mechanism in the single processor real-time system and the multi-processor real-time system, and it produces a static energy management method and a dynamic energy management method of single-processor real-time system, proposes several tasks scheduling algorithms of multi-processor real-time system based on static energy management, then gives the analysis and comparison about these algorithms.