核分组的多核处理器优化方法

随着多核处理器规模的扩大,请求数据的处理器核到数据的宿主节点之间的平均距离相应增大,并且数据访问在分布式共享高速缓存块中的分布并不均衡引起了网络热点。这些情况导致一级高速缓存缺失延迟的增大。为了解决该问题,将每四个处理器核分为一组,在组内设计邻近数据探测器。邻近数据探测器通过确定一次缺失能否在邻近核的一级高速缓存中得到数据,从而利用了并行程序在多核处理器上执行时数据访问的核间局部性。另外,根据新的结构相应优化了高速缓存一致性协议。实验表明,该片上存储优化方法提高了系统性能,减少了片上网络流量,节省了能耗。     

一种软硬件协同控制的片上缓存功耗优化方法

片上多处理器系统的发展导致片上高速缓存的所占面积急剧增加,其对应的泄露功耗也相应增加。将高速缓存行划分成3部分进行控制,其中数据部分的访问分为协议访问和数据访问两部分,每部分支持多种工作模式来进行管控。通过工作模式的切换对高速缓存的三部分进行管控可以使漏过功耗平均减少76.78%,但相应的性能损失最高会达到7.74%。由于性能损失较大,提出了一种改进的高速缓存衰退的方法来优化管控策略。这种策略不仅能够把性能损失控制在3%以下,而且能够保证平均能耗优化达到近75%。     

快速地址计算的自适应栈高速缓存

随着存储系统的访问速度与处理器运算速度的差距越来越显著,访存性能已成为提高处理器性能的瓶颈.通过对程序的访存行为进行分析,提出快速地址计算的自适应栈高速缓存方案.该方案将栈访问从数据高速缓存的访问中分离出来,充分利用栈空间数据访问的特点,提高指令级并行度,减少数据高速缓存污染,降低数据高速缓存失效率,并采用快速地址计算策略,减少栈访问的命中时间.该栈高速缓存在发生栈溢出时能够自适应地关闭,以避免栈切换对处理器性能的影响.栈高速缓存标志中增加进程标识,进程切换时不需要将数据写到低层存储系统中,适用于多进程环境.SPEC CPU2000程序运行结果表明,采用快速地址计算的自适应栈高速缓存方案,25.8%的访存指令可以并行执行,数据高速缓存失效率平均降低9.4%,IPC值平均提高6.9%.     

在NS2中植入新的802．11接入算法的研究

IEEE802．11是目前广泛应用的无线局域网协议标准。它的MAC层协议主要解决在多个用户之间分配信道资源的问题，通过有效的介质访问机制，提高资源的使用率和网络的性能。     

基于循环的指令高速缓存访问预测方法

为了减少高速缓存访问功耗,提出了一种针对循环的基于历史访问路径的指令高速缓存访问预测方法。该方法以循环作为高速缓存访问路预测行为开启的先决条件,通过指令高速缓存的历史访问路径训练预测器。当循环体再次进入时选择对应的访问路径预测器,获取目标指令高速缓存的路进行访问,降低访问功耗。并进一步提出多路径路预测方法,以得到更高的预测准确率。基于Powerstone测试基准的实验结果表明,该预测方法能达到99%的预测准确率。相比传统的指令高速缓存,使用本方法的高速缓存可平均降低65%的访问功耗,仅增加约0.2%的平均指令高速缓存访问周期。     

基于FC-SW存储区域网络的存储系统性能

分析FC-SW存储区域网络(SAN)的网络拓扑结构以及RAID等相关内容,描述在FC-SW SAN中的数据访问流程,在抽象FC-SW SAN的基础上利用排队理论对FC-SW SAN中的存储性能进行分析。阐述磁盘高速缓存命中率、I/O访问读写概率以及网络交换机FC-SW对I/O响应时间的影响。     

网络并行机群文件系统的协同高速缓冲技术研究

XFS文件系统采用了许多用于高性能多处理器设计的技术和协同高速缓存技术。为了更好地确定文件或数据块在工作站机群中的位置 ,XFS采用分层结构来组织宿主机。XFS通过采用回写式高速缓存相关协议 ,解决高速缓存相关性。由于XFS灵活巧妙且充分地利用了局部的宿主机和局部的存储设备 ,所以XFS比当前用于广域网中文件系统更有效且拥有更好的性能。     

基于路访问轨迹的指令高速缓存低功耗策略

现代嵌入式处理器中指令高速缓存的功耗十分显著,对此提出一种基于路访问轨迹的组相联指令高速缓存的低功耗策略,利用改进的指令高速缓存和转移目标缓存建立和维护运行时指令高速缓存的路访问轨迹来减少指令高速缓存命中检测及无关路访问.进一步提出了基于跨行访问前驱指针、转移前驱状态、转移前驱指针及转移目标索引的路访问轨迹信息维护策略用以降低信息重建的频度,从而更有效地利用已建立的路访问轨迹信息.实验结果表明:采用优化后的路访问轨迹策略的指令高速缓存的标志存储器访问和数据存储器访问分别降低到传统指令高速缓存的3.60％和27.70％.     

基于Simics的分布式一致性协议仿真

用于多种计算机系统和指令系统仿真的Virtutech Simics只提供一个简单的顺序扁平侦听式高速缓存一致性（Snoo-ping Cache Coherence Protocol）模型支持MESI协议,从而制约了可仿真的并行处理器个数。以下将基于目录的分布式高速缓存一致性协议（Distributed Directory-based Cache Coherence Protocol）模型应用于Simics中并给出基于Simics的分布式一致性协议的仿真结果。这一结果证实分布式协议能降低事件总数,减少网络中的事件。本文提出一个简单的基于目录的分布式高速缓存一致性协议,从而解决制约Simics的可扩放性问题。     

Pentium系统采用SSRAM／SDRAM存储器的性能分析

ＳＤＲＡＭ，ＳＳＲＡＭ对于平衡存储器和ＣＰＵ的带宽，实现主存的猝发访问，提高系统性能价格比有重要意义，本文基于Ｐｅｎｔｉｕｍ处理器，讨论了高速缓存和主存采用ＳＳＲＡＭ，ＳＤＲＡＭ的不同系统实现方法及相对性能，不同的系统实现就是在性能，价格和设计复杂性之间的取舍，此分析同样适用于任何嵌入式一级高速缓存的处
处理器。     

分布式合作缓存中的全局向量时钟模型

在分布式合作缓存技术对中文件块的查找与替换是一个全局性的管理问题。针对在中系统中由于局部时钟不一致而造成的块查找与块替换决策失误的问题。本文提出了全局向量时钟模型ＧＶＴ的概念,并通过维护基于全局向量的最老时戳表来完成块查找与块替换操作。全局向量时钟对传统的向量时钟进行了改进,提供了多种方式用于时序关系的判断。     

工作站网络上协作任务的调度

在利用工作站群集系统进行的协作模式并行计算中，任务调度在很大程度上决定并行计算的性能．本文给出了一个任务调度的模型和算法，它考虑了协作模式并行计算中任务间的同步时间、通信时间、数据加载及结果收集时间．根据这个调度模型，可以选择一组并行执行时间最短的工作站，从而获得较好的并行计算性能．     

一种基于结点的分布式合作缓存管理算法DCC

工作站机群系统需要有一个高性能的并行文件系统以适用高速输入、输出数据处理的要求,而提高并行文件系统的关键是合作缓存技术。文中提出了一种基于结点的分布式合作缓存管理算法ＤＣＣ。该算法综合了避管理器和基于局部信息两种算法的优点,给出了一种位于结点机上的主块信息站的方法,通过对主块信息站的信息进行维护来达到对全局信息的跟踪。算法采用积极的局限信息维护策略,提高了主块位置判断的准确性。与ＧＭＩＳ算法、Ｈｉ     

Real-time radiology--new concepts for teleradiology

We propose two new concepts for teleradiology: 'real-time radiology' and 'seamless operation of a workstation to view images from both local and remote hospitals'. In this paper, we describe an experimental real-time radiology system with a new multimedia diagnostic workstation, which has been established under teleradiology concepts and can be used for cooperative diagnosis by interchanging radiographic images bilaterally in real-time during an audio-visual discussion. The clinical evaluation of real-time radiology using a newly developed diagnostic workstation demonstrated the system to be practical and routinely available to enhance the radiological diagnostic quality of teleradiology.     

Modeling and control of workstation level information flow in FMS using modified Petri nets

A flexible manufacturing system (FMS) has a traditional structure of three levels: cell, workstation, and equipment. The workstation level plays an important role in the overall performance of the FMS. This paper focuses on modeling and control of the FMS workstation level information flow. In order to have a unified workstation level system structure, front-end interfaces are introduced as a standard communication medium between the workstation level and the equipment level. A detailed information flow analysis is then carried out on the workstation level. For modeling purposes, a modified Petri net is proposed with its increased modeling capability over an ordinary Petri net. It associates data structures with places and programs with transitions. Finally, the modified Petri net is used to model and control the FMS workstation level information flow. The designed control system has been implemented in a real manufacturing factory with satisfactory performance.     

A concurrent network architecture for cost-efficient parallel computing using workstation clusters

Within the past few years, workstation clusters have gained an increasing importance as platforms for parallel high-performance simulation problems. In contrast to the specialized and cost-intensive interconnection network of distributed memory multiprocessor systems, workstation clusters utilize local area networks (LANs) and common communication protocols. Therefore, the cost-efficiency of workstation clusters for parallel tasks is high while the communication performance is limited compared to parallel computer systems. To improve the communication performance of clusters, new protocols can be applied as well as specialized interconnection networks. On one hand, these solutions decrease the cost-efficiency of clusters, while on the other hand the performance of local area networks is increasing because of new technologies such as FastEthernet, GigaEthernet or ATM. In this contribution, we propose increasing the communication performance of clusters through the concurrent network architecture (CNA) with multi-channel communication systems. Through the use of parallel and independent LANs, the communication performance of a cluster can be improved while maintaining the cost-efficiency of the wide-spread LAN technology and protocols. This paper gives an overview of the CNA, the requirements of an implementation and a performance evaluation of a CNA workstation cluster.     

全自动空间水切割机器人系统设计

随着水射流切割技术的发展与应用推广,其边缘技术也逐步走向成熟,为了提高设备的自动化程度,解决水射流切割过程中的控制问题,本文介绍了一种全自动空间水射流切割机器人系统,设计了基于ABB六自由度机器人的水射流切割工作站,阐述了系统的硬件组成和工作原理,并讨论了切割程序结构和切割工艺.实践证明该系统运行稳定,能满足系统性能指标要求.     

CSCW系统访问控制模型及其基于可信计算技术的实现

现有的CSCW访问控制策略模型缺少时间和约束特性,在实现上也未能较好地解决开放网络下的身份伪装和欺骗问题,以及影响安全策略完整性实施的软硬件平台可信问题。本文基于角色一活动概念提出了一种具有时间依赖和约束特征的CSCW访问控制模型Fine-grained Access Control for CSCW,从而能够定义更为精确细致的安全策略;在模型实现中给出了Trusted Computing-enabled Access Control架构以及关键的策略分发和实施协议等。该方法通过建立完整的协作实体-CSCW平台-应用信任链,构建了可信的访问控制平台,增强了协作实体的身份鉴别,并通过角色相关策略的分发和在本地协作站点上的完整性实施,减轻了服务器端集中式执行安全策略的负担。     

Adaptive and Reliable Paging to Remote Main Memory

Workstation clusters provide significant aggregate amounts of resources, including processing power and main memory. In this paper we explore the collective use of main memory in a workstation cluster to boost the performance of applications that require more memory than a single workstation can provide. We describe the design, simulation, implementation, and evaluation of a pager that uses main memory of remote workstations in a workstation cluster as a faster-than-disk paging device and provides reliability in case of single workstation failures and adaptivity in network and disk load variations. Our pager has been implemented as a block device driver linked to the Digital UNIX operating system, without any modifications to the kernel code. Using several test applications we measure the performance of remote memory paging over an Ethernet interconnection network and find it to be up to twice as fast as traditional disk paging. We also evaluate the performance of various reliability policies and demonstrate their feasibility even over low bandwith networks such as Ethernet. We conclude that the benefits of reliable remote memory paging in workstation clusters are significant today and are likely to increase in the near future.     

Affective Temperature Control in Food SMEs using Artificial Neural Network

This paper highlights modeling affective temperature control in food small and medium-sized enterprises (SMEs). Modeling defined that workstation temperature set point could be controlled based on worker heart rate and workstation environment using Artificial Neural Network (ANN). The research objectives were: 1) to propose modeling affective temperature control in food SMEs based on heart rate and workstation environment; and 2) to develop an ANN model for predicting workstation temperature set point. Training and validation data were collected from six food SMEs in Yogyakarta Special Region, Indonesia. The data of temperature set points were verified using a simulated confined room. The inputs of the ANN model were worker heart rate, workstation temperature, relative humidity distribution and light intensity. The output was temperature set point. Research results concluded satisfactory performance of ANN. The model could be used to provide environmental ergonomics in food SMEs.