Performance analysis of advanced I/O architectures for PC-based video servers

In the personal computing and workstation environments, more and more I/O adapters are becoming complete functional subsystems that are intelligent enough to handle I/O operations on their own without much intervention from the host processor. The IBM subsystem control block (SCB) architecture has been defined to enhance the potential of these intelligent adapters by defining services and conventions that deliver command information and data to and from the adapters. In recent years, a new storage architecture, the redundant array of independent disks (RAID), has been quickly gaining acceptance in the world of computing. In this paper, we discuss and present a performance analysis of the SCB architecture and disk array technology in typical video server environments. In particular, we would like to see whether a disk array can outperform a group of disks (of the same type, the same data capacity, and same cost) operating independently (not in parallel as in a disk array) in a video server environment where most disk I/O operations are large sequential reads.     

A performance analysis of an object-based I/O architecture in a video server environment

In this paper, we present a performance analysis of how effective video server applications can be supported on personal computers (PCs) connected through a local area network (LAN). We considered both the standard 16-Mbit/s token ring and a 100-Mbit/s token ring, which follows closely the specifications for the Fiber Distributed Data Interface (FDDI). We examined three I/O architectures for a PC-based video server: an interrupt-driven I/O architecture, a peer-to-peer I/O architecture, and a concurrent, object-based I/O architecture that we proposed. The video server must support multiple MPEG-1 video streams at the same time to multiple clients on the LAN. We found that the network protocol layers require a lot of processing power, and that an implementation of our proposed I/O architecture, which takes advantage of the available power of the host processor to off-load I/O adapters, can deliver much better performance, and is more cost-effective, than other I/O architectures in a video server environment.     

Performance analysis of a peer-to-peer I/O architecture in video server environments

In the personal computing (PC) and workstation environments, more and more I/O adapters are becoming complete functional subsystems that are intelligent enough to handle I/O operations on their own without much intervention from the host processor. The IBM Subsystem Control Block (SCB) architecture has been defined to enhance the potential of these intelligent adapters by defining services and conventions that deliver command information and data to and from the adapters. The SCB architecture has two operating modes. The Locate Mode represents the conventional, interrupt-driven I/O protocol used in many current personal computers. The Move Mode embodies an advanced, peer-to-peer I/O protocol proposed for the next generation of personal computers. In this paper, we would like to discuss and present a performance analysis of the SCB architecture in typical video server environments. In particular, we study a video server capable of providing support for simultaneous MPEG-1 video streams to multiple clients on a 16-Mbps token-ring network. We also consider the performance impact of a hypothetical 100-Mbps token-ring technology on the video server performance.     

RISC微处理器中I/O子系统设计的一种优化方法

低效率的访存操作是限制微处理器性能提高的一个关键因素。提出了I/O子系统（IOSS）设计中一种优化的模型,阐述了该模型提高访存效率的机制,分析了这种模型协调微处理器与存储器之间速度差异的作用。Verilog仿真、综合和静态时序分析的结果表明该设计达到了预定的要求。目前龙腾Ⅱ微处理器已经进入后端流程,不久将使用0.18μm的工艺进行流片。     

Beacon+：面向E级超级计算机的轻量级端到端I/O性能监控与分析诊断系统

随着E级计算的屏障被打破,高性能计算已经迈入了新时代。为了满足日益增长的数据访问需求,新兴的技术和存储介质都被运用到了超级计算机中,这使得其架构变得日趋复杂,其性能异常和系统热点定位也变得十分困难。为此,设计并实现了一个面向E级超级计算机的轻量级端到端I/O性能监控与分析诊断系统——Beacon+。该系统无需修改应用代码/脚本即可对每个应用的数据访问过程进行全路径实时监控与分析。通过在线+离线的压缩方法和分布式缓存/存储等机制,Beacon+在保证系统本身高扩展性、低开销的同时还可以持续稳定地提供I/O诊断服务。以神威新一代超级计算机为部署平台,通过I/O标准测试应用和实际应用证明了Beacon+的低开销和高准确性,以及I/O诊断的高效性。     

基于PLC控制的自动化移载机的开发设计

介绍了移载机的用途、工作原理,阐述了其基于PLC控制的机械结构和电气结构设计思想。实际运行表明:设计的自动化移载机硬件结构简单合理、运行稳定、软件升级容易。     

压缩对Hadoop性能影响研究

当今,磁盘I/O的发展速度永远赶不上遵照摩尔定律的CPU的发展速度,并且网络I/O资源稀缺,所以I/O常常成为数据处理的瓶颈。Hadoop能存储PB级数据,因此I/O问题愈加显著。压缩是I/O调优的一个重要方法,它能减少I/O的负载,加快磁盘和网络上的数据传输。首先通过分析Hadoop中各压缩算法的特点,得出一个压缩使用策略来帮助Hadoop的使用者确定如何使用压缩,并用实验得以验证补充。基于该策略,一些Hadoop应用在合理使用压缩后,效率能提高65%。     

Prioritisation of public investments in social infrastructures using multicriteria value analysis and decision conferencing: a case study

Not‐for‐profit private organisations that provide social services to children, the elderly and the disabled apply for financial support to develop or to renew their social infrastructures, through the Portuguese Institute for Social Welfare. In the context of scarce financial resources, the Institute decision‐makers felt the need to adopt an improved “rationality” in resource allocation, in order to increase transparency and to ensure that the collective best use is made of a limited budget. This paper describes the socio‐technical process followed in building a multicriteria value model, under a decision conferencing framework in which participation and interaction among decision‐actors were key features in the development of the three main phases of problem structuring, evaluation and prioritisation.     

并行数据库系统中并行I／O的研究与实现

并行Ｉ／Ｏ是基于无共享结构的并行数据库系统提高性能的有效途径之一。它通过并行磁盘服务和网络传输并行化提供了高带宽Ｉ／Ｏ。文章设计实现了基于无共享结构的并行数据库系统的并行Ｉ／Ｏ,探讨了设计并行Ｉ／Ｏ时的几个关键问题及实现技术。     

Trace生成对大规模并行性能模拟的影响及其改进策略

Trace生成是trace驱动体系结构模拟中不可或缺的步骤。Trace不仅需要占用大量存储空间,其生成过程还可能对目标应用程序的模拟执行产生一定程度的干扰,导致性能数据误差。Trace驱动并行性能模拟器由于其设计实现特点和所运行的宿主并行平台的多样性,使得trace生成的影响具有其独特性。本文选取典型并行模拟器BigSim和若干具有不同计算通信比的目标并行程序,在三个支持不同traceI/O方式的宿主机平台上设计实验评估了trace生成对并行性能模拟的影响,结果表明trace生成对模拟效率和精度均有较大的影响,并分析了这种影响与并行模拟器实现和宿主机平台I/O方式的关系,进而讨论了几种可行的改进方案,对trace驱动并行模拟器设计、实现和使用具有一定的指导意义。     

一种集群计算系统中并行I/O文件存储分配策略

现代计算机系统性能已经由受限于CPU转变为受限于I／O，近年来研究人员对高性能计算中的并行I／O问题进行了深入研究．本论文的主要工作是对集群计算中的并行I／O子系统进行研究，提出一种文件拆分与存储分配的新策略，即：已知知识的文件拆分与分配方法(KKFDA)，该方法保证文件存储方式与访问方式的一致性，达到了提高文件访问时的本地命中率、缩短访盘响应时间的目的．算法设计与实验证明了方法的有效性．     

节省PLC控制系统I／O点数的实用方法

介绍了几种简单的节省PLC控制系统I／O点数的方法，运用这些方法可以实现小型PLC控制较大系统，从而降低设备投资，具有实用价值。     

通用分布式仿真I/O体系结构设计及其应用

分析了几种典型仿真I/O体系结构的优缺点,设计并实现了一种软硬件可伸缩的分布式 仿真二级I/O体系结构,该结构不仅直接支持了共享的时分多路通道存取型数字设备(如7段数码管 显示器),将硬联逻辑复杂度从O(n)降低到O(logn)的水平,而且具有实时性、可伸缩性、容错性、可 维护性和通用性等良好特征,较好地满足了半实物仿真系统的需要。     

大型DCS轮机仿真I/O接口系统研究

I／O接口系统的性能直接关系到轮机仿真系统的实时性和稳定性，需要对其进行深入研究。文章介绍了作者自主研制开发的分布式轮机仿真I／O接口系统的组成。讨论了其各硬件板卡的设计，分析了该系统的数据通信原理。系统实际应用表明，该系统特别适用于大型、复杂的系统仿真。     

一类非线性时滞系统的解耦控制

利用微分几何方法研究了一类非线性多输入多输出时滞系统的解耦问题．讨论了此类系统可解耦的充分条件，并给出了此类系统实现输入/输出间精确线性化的条件以及其标准形．文中给出了非线性时滞系统得以解耦的非线性状态反馈控制律；此状态控制律不但可以实现输出与时滞状态变量的解耦，还可以实现输出与输入间的精确线性化．而其闭环标准形的给出为此类系统实现各种控制目标带来了方便．     

InTouch9．0在电厂输煤程控系统中的应用

根据电厂输煤基本原理，提出了应用InTouch9．0软件设计某电厂输煤程控系统的方法，介绍了系统的设计，生产过程中的数据显示、记录、处理和报警，以及InTouch9．0通信原理和配置。实现了对系统控制、维护与管理的集成。     

A sparse matrix scheme for the computer analysis of structures

Many matrix formulations of structural analyses involve matrices having a large proportion of zero elements. By storing only the non-zero elements of all matrices, machine store and time may be utilised effectively, making the simplest matrix formulations feasible as a method of computer solution even for fairly large frame problems. The method of operation of some sparse matrix routines written for use on the Atlas Computer is briefly described and their application to some frame problems is discussed. The term “searching factor” is introduced as a guide to the efficiency of sparse matrix routines.     

Merging video streams in a multimedia storage server: complexity and heuristics

Due to recent advances in network, storage and data compression technologies, video-on-demand (VOD) service has become economically feasible. It is a challenging task to design a video storage server that can efficiently service a large number of concurrent requests on demand. One approach to accomplishing this task is to reduce the I/O demand to the VOD server through data- and resource-sharing techniques. One form of data sharing is the stream-merging approach proposed in [5]. In this paper, we formalize a static version of the stream-merging problem, derive an upper bound on the I/O demand of static stream merging, and propose efficient heuristic algorithms for both static and dynamic versions of the stream-merging problem.     

实时数据库调度策略综述

该文对实时数据库系统的调度策略进行了较为全面的介绍与评述。综述的调度策略包括三个方面:安排事务优先级、并发控制和I/O调度。文章详细介绍和评价了每个方面的处理原则、典型算法和派生算法,并对调度策略今后的发展方向进行了展望。