Real-time dynamic voltage scaling for low-power embedded operating systems

Abstract

In recent years, there has been a rapid and wide spread of nontraditional computing platforms, especially mobile and portable computing devices. As applications become increasingly sophisticated and processing power increases, the most serious limitation on these devices is the available battery life. Dynamic Voltage Scaling (DVS) has been a key technique in exploiting the hardware characteristics of processors to reduce energy dissipation by lowering the supply voltage and operating frequency. The DVS algorithms are shown to be able to make dramatic energy savings while providing the necessary peak computation power in general-purpose systems. However, for a large class of applications in embedded real-time systems like cellular phones and camcorders, the variable operating frequency interferes with their deadline guarantee mechanisms, and DVS in this context, despite its growing importance, is largely overlooked/under-developed. To provide real-time guarantees, DVS must consider deadlines and periodicity of real-time tasks, requiring integration with the real-time scheduler. In this paper, we present a class of novel algorithms called real-time DVS (RT-DVS) that modify the OS's real-time scheduler and task management service to provide significant energy savings while maintaining real-time deadline guarantees. We show through simulations and a working prototype implementation that these RT-DVS algorithms closely approach the theoretical lower bound on energy consumption, and can easily reduce energy consumption 20% to 40% in an embedded real-time system. Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies boar this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. SOSP01 Banff, Canada ful microprocessors running sophisticated, intelligent control software in a vast array of devices including digital camcorders, cellular phones, and portable medical devices.

Energy performance evaluation for dynamic frequency scaling on rate monotonic and earliest deadline first scheduling algorithm

“…It may affect the processing speed when there are few active tasks causing them finished after deadlines if additional task arrives. Pillai and Shin (2001) introduced five algorithms considering both EDF and RM schedulers. All the algorithms only consider periodic task and set the speed at the lowest speed that guaranteed execution time of the task.…”

Real-Time Dynamic Voltage Scaling for the EPOS Operating System

“…Ao mesmo tempo que devem economizar energia, ganham a responsabilidade sobre tarefas inteligentes que necessitam de processamento poderoso. Mesmo com a exigência de alto desempenho, o pico da demanda de computação costuma acontecer apenas em alguns momentos do funcionamento de sistemas de tempo real [1]. Em sistemas dedicados, onde se tem um maior conhecimento sobre o comportamento das aplicações, tem-se encontrado um palco interessante para a aplicação de técnicas de DVFS em sistemas de tempo real, também chamadas de RT-DVFS.…”

“…Pela seleção da frequência ser realizada anteriormenteà execução do conjunto de tarefas, o novo algoritmo tornase fracamente acoplado ao escalonador de tempo real [1]. Isto significa que uma configuração prévia do sistema pode ser feita e, em tempo de execução, um escalonador EDF comum pode ser empregado.…”

“…Dos trabalhos que desenvolvem implementações reais de suporte a RT-DVFS, comumente as demonstrações ocorrem em sistemas Linux com a adição de módulos ou extensões [1], [3], [4], [2]. O sistema operacional EPOS, onde realizamos nossa implementação, já possui suporte nativo a tarefas de tempo real [5].…”

“…As heurísticas para RT-DVFS Static Voltage Scaling e Cycle-conserving para o escalonador EDF [1] são utilizadas como estudo de caso para avaliação do ambiente criado.…”