基于程序段的可重构cache与处理器低能耗算法*

运用可重构cache和动态电压缩放技术,为处理器及其cache提出了一种基于程序段的自适应低能耗算法PBLEA（phasebased low energy algorithm）。该算法使用建立在指令工作集签名基础上的程序段监测状态机来判断程序段是否发生变化,并作出cache容量及CPU电压和频率的调整决定。在程序段内,使用容量调整状态机和通过计算频率缩放因子β来先后对cache容量及CPU电压和频率进行调整。在Simpanalyzer模拟器上完成了该算法的实现。通过对MiBench测试程序集的测试表明     

动态时间片缩放:一种优化Linux 任务公平性的方法

处理器动态电压频率调节技术,对Linux系统中并发任务的性能产生不同程度的变化,从而影响并发任务计算资源分配的公平性.提出了一种利用动态时间片缩放来优化任务公平性的方法,并基于Linux操作系统任务调度程序,加入动态时间片缩放模块,该模块通过读取CPU性能监控计数器,在线计算时间片缩放系数,并利用该系数对任务时间片长度进行动态缩放.实验表明,这种方法以较小的系统开销为价,极大地提高了Linux中并发任务计算资源分配的公平性.     

一种基于电压岛的DVFS控制算法

提出一种基于岛间队列特征的动态电压频率缩放控制算法,使用岛间队列增长率和使用率来实现电压岛工作电压/频率的动态控制.该算法引入岛间队列增长率实现了简单高效的负载预测,提高了片上通信稳定性.仿真分析表明,该算法能够更好地节能降耗.     

一种新的基于动态电压调整的单任务调度方法

合理运用动态电压调整技术可以有效降低实时任务运行所需的能耗.提出了一种新的单任务DVS调度方法,针对程序的平均执行信息,并结合参数化动态预测策略,合理设置电压/频率调整点.实验结果表明,该方法能够充分利用动态松弛时间,有效控制调整开销,实现较高的能耗优化率.     

针对离散电压处理器的动态电压调节策略

嵌入式系统设计者在以往设计过程中,通常只考虑到系统的稳定性、实时性等,但现在却面临着一个新的挑战降低系统的功耗.基于LP线性规划模型,针对具有离散工作电压模式的处理器提出了一种动态电压调节策略LPBVSP(LP based voltage scaling policy).LPBVSP能够根据工作负载的需求变化实现处理器...     

一种低功耗动态可重构cache算法的研究

动态可重构cache算法根据指令时间数监测程序段的变化,确定容量调整.在程序段内,状态机根据平均访问时间对cache的访问进行预判,然后根据预判的结果确定当前程序段的cache结构.实验结果表明,此算法比传统四路组相联cache功耗降低61％,而性能损失只有2％左右.与已有算法相比,功耗和性能都得到进一步的提高.     

基于动态电压调节技术的系统功耗优化

分析了现有动态电压调节算法，提出了改进算法的频率设置部分，以提高算法的性能，并在Linux系统上实现了这些算法。经过在物理平台上的测试，表明改进算法能够在不影响性能的情况下减少系统能量消耗。     

一种用于动态电压恢复器的电压跌落检测算法

针对传统的电压跌落d-q检测算法和Hilbert检测算法在补偿快速性和抗干扰性方面存在矛盾的问题,提出了一种将d-q检测算法与Hilbert检测算法相结合的电压跌落检测新算法:对电网侧电压信号采样后,经d-q检测单元得到谐波补偿波形;然后滤除3次谐波,滤波后的信号再经Hilbert检测单元得到电压幅值补偿波形;叠加该2种补偿波形可确定最终的补偿波形。仿真结果表明,该检测算法对于含3次谐波的电压跌落补偿效果较好,兼具补偿快速性和抗干扰能力。     

实时系统中混合任务集的动态电压调节算法

在实时嵌入式系统中,核心处理器的能耗占据整个能耗的相当大一部分.动态电压调节被看作是降低处理器能耗的关键技术,介绍实时系统和动态电压调节的基本概念,并在CMOS器件功耗理论和实时系统下任务调度理论的基础上,提出基于混合任务集的减慢因子DVS算法.     

基于语法树的实时动态电压调节低功耗算法

动态电压调节是一种有效的低功耗技术.使用这种技术,编译器指导的动态电压调节能够有效地降低系统功耗.提出了基于语言语法树的实时动态电压调节低功耗算法.该算法在静态程序最差时间分析方法的辅助下,通过在程序内部自动插入电压调节代码来实现电压调节.在RTLPower(real-time low-power)实时低功耗系统上完成了算法的实现,对嵌入式测试,程序集的初步测试证明该算法最大可节省50%的能量消耗.     

一个基于资源操作的强实时动态调压算法

动态调压算法能够降低系统功耗，可用来降低CPU发热量、延长电池供电系统的工作时间．然而，现有动态调压算法均不允许进程进行资源操作（申请或释放资源），这在实际应用中是难以满足的．因此，现有算法不便于实际应用,本文提出了一种新的强实时动态调压算法．该算法允许进程进行资源操作，并且功耗低于现有算法；该算法还能避免死锁．该算法易于应用到实际系统中．     

CPU频率对电池的影响以及对动态调压算法的改进

对电池供电的嵌入式系统来说，电池工作时间是重要的指标．利用动态调压算法对CPU频率进行调度．可以延长电池工作时间．然而，目前尚没有通用的方法对CPU频率和电池之间的关系进行深入研究，这导致动态调压算法不能最大限度地延长电池工作时间，本文提出一种新方法来研究CPU频率对电池的影响，其结论具有通用性，并得到实验的验证，利用这个结论，本文对动态调压算法进行了优化，使之更适于电池供电系统。     

一种采用动态电压调整的实时节能调度算法

较高的能量消耗会导致处理器热量的增加及系统可靠性的降低,合理运用动态电压调整技术有效降低实时任务运行所需的能耗成为一个研究热点.提出一种动态实时节能调度算法MSF,以最大空闲时间优先调度为基础,结合动态调整技术,使得实时任务在其截止期内完成的同时能够最大限度地降低整个系统的能量消耗.实验结果表明, 该方法能够充分利用任务的不同能量特性和动态空闲时间,更有效的实现节能,优于其它算法.     

基于动态电压调节的低功耗视频解码技术研究

讨论在嵌入式系统中使用动态电压调节技术降低视频解码功耗。提出一种基于动态电压调节的低功耗解码技术。该方法采用移动平均法预测帧的解码时间,依据预测的结果动态地调节解码过程中微处理器的工作电压,降低能量消耗。实验结果表明,基于动态电压调节的视频解码器比常规解码器减少10%￣30%的能量消耗。     

EPTS:一种实时动态电压调整的抢占阈值调度器

低功耗目前已成为嵌入式实时系统设计中非常重要的性能需求。动态电压调度DVS机制通过动态调整处理器电压进而有效降低系统功耗,正在逐渐得到广泛应用。抢占阈值调度策略实现双优先级系统,每个任务具有两个优先级,任务优先级被用于任务之间竞争处理器,而抢占阈值作为任务开始运行后实际使用的优先级,从而减少现场切换次数,降低系统功耗,同时也提高整个任务集合的可调度性。本文提出一种在线节能调度算法EPTS,拓展抢占阈值调度模型,在任务执行过程中动态调节处理器电压,力求在保证任务集合可调度性的前提下尽可能减少系统功耗,提高系统性能。而后在AMDAthlon4处理器和RT-Linux平台上实现了EPTS调度器,实验证明对于实际任务集合能够有效节能,提高了处理器的利用率,改善了RT-Linux的实时性能。     

Dynamic Voltage Scaling for Digital Control System Implementation

For real-time computer-controlled systems, control performances of tasks as well as energy consumption of overall system must be optimized. A control task does not have a fixed period but a range of periods in which the control performance varies. Hence, when more than one control tasks are scheduled on a single processor, an optimization problem appears. Furthermore, when an energy saving technique such as dynamic voltage scaling is used, its properties affect the control performance.Using a performance index that involves control performance and energy consumption, a static solution is proposed to obtain the optimal processor speed and a set of periods for given control tasks in O(k). Also a dynamic solution is proposed to utilize system services of real-time operating systems to overcome unavoidable deficiencies of the static solution and to further reduce the energy consumption of the overall system. The performances of proposed solutions are revealed via simulation studies.Hyung Sun Lee received his B.S. and M.S. degrees in electronics engineering from Korea Advanced Institute of Science and Technology (KAIST) in 2000 and 2002, respectively. He is currently a Ph.D. student in the Department of Electrical Engineering and Computer Science (EECS) at KAIST. His research interests include real-time control and power-aware real-time embedded systems.Byung Kook Kim received his B.S. degree in Electronics Engineering from Seoul National University in 1975, and his M.S. and Ph.D. degrees from KAIST in 1977 and 1981, respectively. Dr. Kim was a manager and founder of the Calibration Laboratory, Woojin Instrument Co. Ltd, in 1981. He performed his postdoctoral research at the University of Michigan, Ann Arbor, Michigan, from 1982 to 1983. He returned to Woojin Instruments as a chief researcher of the R&D Department from 1984 to 1986. He joined the faculty of the Department of Electrical Engineering at KAIST in 1986, where he is currently a professor. His research interests include real-time systems, parallel and distributed systems, fault-tolerant computing, mobile robot sensing and navigation, and manipulator control.     

Feedback EDF Scheduling of Real-Time Tasks Exploiting Dynamic Voltage Scaling

Many embedded systems are constrained by limits on power consumption, which are reflected in the design and implementation for conserving their energy utilization. Dynamic voltage scaling (DVS) has become a promising method for embedded systems to exploit multiple voltage and frequency levels and to prolong their battery life. However, pure DVS techniques do not perform well for systems with dynamic workloads where the job execution times vary significantly. In this paper, we present a novel approach combining feedback control with DVS schemes targeting hard real-time systems with dynamic workloads. Our method relies strictly on operating system support by integrating a DVS scheduler and a feedback controller within the earliest-deadline-first (EDF) scheduling algorithm. Each task is divided into two portions. The objective within the first portion is to exploit frequency scaling for the average execution time. Static and dynamic slack is accumulated for each task with slack-passing and preemption handling schemes. The objective within the second portion is to meet the hard real-time deadline requirements up to the worst-case execution time following a last-chance approach. Feedback control techniques make the system capable of selecting the right frequency and voltage settings for the first portion, as well as guaranteeing hard real-time requirements for the overall task. A feedback control model is given to describe our feedback DVS scheduler, which is used to analyze the system's stability. Simulation experiments demonstrate the ability of our algorithm to save up to 29% more energy than previous work for task sets with different dynamic workload characteristics. This work was supported in part by NSF grants CCR-0208581, CCR-0310860 and CCR-0312695. Preliminary versions of parts of this work appeared in the ACM SIGPLAN Joint Conference Languages, Compilers, and Tools for Embedded Systems (LCTES'02) and Software and Compilers for Embedded Systems (SCOPES'02) (Dudani et al., 2002), in the Workshop on Compilers and Operating Systems for Low Power 2002 (Zhu and Mueller, 2002) and in the IEEE Real-Time Embedded Technology and Applications Symposium 2004 (Zhu and Mueller, 2004a).     

低能耗软件设计中的性能无损电压调度技术研究

合理地运用动态电压调整技术可以有效降低软件运行所需的能耗·从归纳分析电压调整特征入手,针对程序执行中存在电压调整特征差异的情况,提出了性能无损的低能耗电压调度问题·把该问题形式化为一个混合整数规划模型(MILP),提出了基于剖析结果的PGS算法和基于分析结果的ADS算法·实例分析表明所提出的方法能够有效实现性能无损的低能耗软件设计,模拟实验表明启发式算法可实现较好的近似解·