Tardiness bounds under global EDF scheduling on a multiprocessor

We consider the scheduling of a sporadic real-time task system on an identical multiprocessor. Though Pfair algorithms are theoretically optimal for such task systems, in practice, their runtime overheads can significantly reduce the amount of useful work that is accomplished. On the other hand, if all deadlines need to be met, then every known non-Pfair algorithm requires restrictions on total system utilization that can approach approximately 50% of the available processing capacity. This may be overkill for soft real-time systems, which can tolerate occasional or bounded deadline misses (i.e. bounded tardiness). In this paper we derive tardiness bounds under preemptive and non-preemptive global EDF}$" align="middle" border="0"> when the total system utilization is not restricted, except that it not exceed the available processing capacity. Hence, processor utilization can be improved for soft real-time systems on multiprocessors. Our tardiness bounds depend on the total system utilization and per-task utilizations and execution costs—the lower these values, the lower the tardiness bounds. As a final remark, we note that global EDF}$" align="middle" border="0"> may be superior to partitioned EDF}$" align="middle" border="0"> for multiprocessor-based soft real-time systems in that the latter does not offer any scope to improve system utilization even if bounded tardiness can be tolerated.

EDF调度算法可调度性分析方法的改进研究

任务集的可调度性分析是实时系统研究和应用的关键问题。针对抢占式与不可抢占式EDF(earliest deadline first)调度算法, 分别给出了实时任务集新的可调度性测试条件, 针对任务集为可调度时可以实现快速判定。通过与已有的EDF算法的可调度性判定充要条件相结合, 提出了改进的抢占式与不可抢占式EDF算法的可调度性分析方法。仿真实验表明, 相对现有EDF算法的可调度性分析方法, 所提出的方法能有效提高算法性能。     

基于并行SMS结构的可开关可调谐掺铒光纤激光器

提出了一种基于并行单膜光纤(SMF)-多膜光纤(MM F)-SMS(SMS)结构的可调谐掺铒光纤(EDF)激光器,其总体结构是在环形激光腔中 采用了两个并行的SMS结构作为滤波器件。通过控制腔内的损耗,具有单、双波长 可 开关特性。单、双波长状态下的边模抑制比(SMSR)均大于35dB 。波长调谐采用弯曲调谐的方式, 单波长状态下,当螺旋测微计控制的位移量从0μm变化到60μm时 ,输出激光中心波长从 1558.3nm变化到1557.3nm。实验结果表明,此结构的光纤激光器不仅具有结构简单、成本 低的优点,还具有波长可开关和可调谐特性,在波分复用(WDM)光通信系统、光纤传感和高 精度光谱测量等众多领域有着很好的应用前景。     

A Method for Performance Analysis of Earliest-Deadline-First Scheduling Policy

This paper introduces an analytical method to approximate the fraction of jobs missing their deadlines in a soft real-time system when the earliest-deadline-first (EDF) scheduling policy is used. In the system, jobs either all have deadlines until the beginning of service (DBS) and are non-preemptive, or have deadlines until the end of service (DES) and are preemptive. In the former case, the system is represented by an M/M/m/EDF+G model, i.e., a multi-sever queue with Poisson arrival, exponential service, and generally distributed relative deadlines. In the latter case, it is represented by an M/M/1/EDF+G model, i.e., a single-server queue with the same specifications as before. EDF is known to be optimal in both of the above cases. The optimality property of EDF scheduling policy is used for the estimation of a key parameter, namely the loss rate when there are n jobs in the system. The estimation is possible by assuming an upper bound and a lower bound for this parameter and then linearly combining these two bounds together. The resulting Markov chains can then be easily solved numerically. Comparing numerical and simulation results, we find that the existing errors are relatively small.     

高平坦C L波段掺Er光纤超荧光光源实验研究

报道了一种980 nm激光二极管(LD)双向泵浦的高功率、高平坦的稳定掺Er光纤(EDF)超荧光光纤光源(ED-SFS),实现了C+L波段放大的自发辐射(ASE)光的输出。光源采用双向LD泵浦11 m高浓度的EDF串接普通EDF。通过数值模拟,得到了一定泵浦功率下优化输出光谱带宽的合适光纤长度为70 m。实验得到系统输出接近70 nm的C+L平坦增益谱,输出最大功率达28 mW,输出功率稳定性优于±0.02 dB。     

一种基于EDF算法的多处理器实时调度算法

多处理器系统实时调度理论是目前实时系统研究的热点问题。EDF调度算法是目前流行的实时调度算法,有很多优点,但在多处理器系统应用中存在问题。论文研究了EDF调度算法在多处理器系统中的调度理论,在此基础上,提出了一种基于EDF算法的优先级驱动实时调度算法,算法充分利用了EDF调度算法的优点,较大程度地克服了EDF算法在多处理器系统中的调度缺点,并提供了较好的实时调度性能。     

法国高电压强电流试验室(二)

（上接2005年第9期P81页） 　2 CERDA开关试验研究中心 CERDA开关试验研究中心创建于1929年.1994年经官方COFRAC认证属Alstom系统,为开关工厂产品服务.他也是法国ESEF强电流室联合体成员之一（共3个,EDF雷纳第中心、CERDA中心与VOLTA中心）,在世界范围内也是STL成员.     

地震卓越频率(EDF)对主动调谐质量阻尼器抗震控制设计的影响评价

基于Kanai-Tajimi地震动模型，建立了设置主动调谐质量阻尼器(ATMD)结构的传递函数。于是，ATMD最优参数的评价准则定义为：设置ATMD结构的最大动力放大系数的最小值的最小化。ATMD有效性的评价准则定义为：设置ATMD结构的最大动力放大系数的最小值的最小化与未设置ATMD结构的最大动力放大系数之比。ATMD冲程的评价准则定义为：ATMD的最大动力放大系数。基于选择的评价准则，研究了地震卓越频率(EDF)对ATMD在控制结构位移响应时的最优参数、有效性和冲程的影响。     

宽带、高稳定掺铒光纤超荧光光源

概述了掺铒光纤超荧光光源的基本原理、主要结构和特点;介绍超荧光光源的最新研究进展,报道我们研制的中心波长稳定的L波段超荧光宽带光源和单级掺铒光纤C L波段超荧光宽带光源。     

EDF调度方法在交换式工业以太网中的实现

针对工业以太网的数据特点 ,通过在以太网数据帧中引入IEEE80 2 .1Q优先级字段来区分周期性实时数据和非实时数据 ,并对前者优先进行传送。同时还在周期性数据帧中引入截止期限字段来区分其不同的紧急程度 ,并对其采用非中断的EDF调度方法来改善周期性数据帧的端到端延迟。最后通过仿真试验验证了该方法的可行性。