基于JavaMail的Web Mail系统的实现

本文提出一个在Solaris平台上以Sendmail、qpopper作为SMTP和POP3服务器,以Oracle高性能数据库为存储系统,以JavaMail、Servlet、JDBC为开发工具,实现高性能的Web Mail系统。由于Java的跨平台性,使该系统具有很好的兼容性和扩展性。     

EJVM: an economic Java run‐time environment for embedded devices

As network‐enabled embedded devices and Java grow in their popularity, embedded system researchers start seeking ways to make these devices Java‐enabled. However, it is a challenge to apply Java technology to these devices due to their shortage of resources. In this paper, we propose EJVM (Economic Java Virtual Machine), an economic way to run Java programs on network‐enabled and resource‐limited embedded devices. Espousing the architecture proposed by distributed JVM, we store all Java codes on the server to reduce the storage needs of the client devices. In addition, we use two novel techniques to reduce the client‐side memory footprints: server‐side class representation conversion and on‐demand bytecode loading. Finally, we maintain client‐side caches and provide performance evaluation on different caching policies. We implement EJVM by modifying a freely available JVM implementation, Kaffe. From the experiment results, we show that EJVM can reduce Java heap requirements by about 20–50% and achieve 90% of the original performance. Copyright © 2001 John Wiley & Sons, Ltd.     

Client ahead‐of‐time compiler for embedded Java platforms

Many embedded Java platforms execute two types of Java classes: those installed statically on the client device and those downloaded dynamically from service providers at run time. For achieving higher performance, the static Java classes can be compiled into machine code by ahead‐of‐time compiler (AOTC) in the server, and the translated machine code can be installed on the client device. Unfortunately, AOTC cannot be applicable to the dynamically downloaded classes. This paper proposes client‐AOTC (c‐AOTC), which performs AOTC on the client device using the just‐in‐time compiler (JITC) module installed on the device, obviating the JITC overhead and complementing the server‐AOTC. The machine code of a method translated by JITC is cached on a persistent memory of the device, and when the method is invoked again in a later run of the program, the machine code is loaded and executed directly without any translation overhead. A major issue in c‐AOTC is relocation because some of the address constants embedded in the cached machine code are not correct when the machine code is loaded and used in a different run; those addresses should be corrected before they are used. Constant pool resolution and inlining complicate the relocation problem, and we propose our solutions. The persistent memory overhead for saving the relocation information is also an issue, and we propose a technique to encode the relocation information and compress the machine code efficiently. We developed a c‐AOTC on Sun's CDC VM reference implementation, and our evaluation results indicate that c‐AOTC can improve the performance significantly, as much as an average of 12% for EEMBC and 4% for SpecJVM98, with a persistent memory overhead of 1% on average. Copyright © 2008 John Wiley & Sons, Ltd.     

可扩展机群资源监控系统的设计与实现

论文主要描述了高性能计算机群的资源系统监控系统FARMON的设计与实现。系统通过使用动态加载技术和相应的动态链接库管理协议,使用户可以灵活地添加新的资源监控功能;系统使用LDAP目录服务器,使得系统能对外发布本地机群的资源信息,实现多个机群的协作以及机群和网格计算环境之间的协作;系统使用JavaApplet实现的客户端提供了机群资源的图形监控功能。     

Babylon: middleware for distributed,parallel, and mobile Java applications

Babylon is a collection of tools and services that provide a 100% Java‐compatible environment for developing, running and managing parallel, distributed and mobile Java applications. It incorporates features such as object migration, asynchronous method invocation, and remote class loading, while providing an easy‐to‐use interface. Additionally, Babylon enables Java applications to seamlessly create and interact with remote objects, while protecting those objects from other applications by implementing access restrictions and separate namespaces. The implementation of Babylon centers around dynamic proxies, a feature first available in Java 1.3, that allow proxy objects to be created at runtime. Dynamic proxies play a key role in achieving the goals of Babylon. The potential cluster computing benefits of the system are demonstrated with experimental results, which show that sequential Java applications can achieve significant performance benefits from using Babylon to parallelize their work across a cluster of workstations. Copyright © 2008 John Wiley & Sons, Ltd.     

Linux机群负载监控系统设计与实现

机群系统的管理,需要通过负载监控系统来了解机群负载状况。本文介绍了为胜利油田计算中心设计和开发的Linux机群负载监控系统。通过读取proc文件系统,获得机群结点的实时运行信息;主监控模块采用Java语言设计,利用Java良好的跨平台性,实现对机群负载的跨平台监控;数据和控制命令通过TCP协议传输,可以在联网的任何一台计算机上对机群进行远程监控。     

InfiniBand集群监控工具CLS的设计与实现

集群的监控和管理工具多种多样,设计方法也有很多,本文综合国内外多种集群系统的性能检测工具设计方法的优点,结合面向对象设计思想,主要对Infiniband网络性能监控和并行程序监控进行改进,在RedhatLinux系统下使用C语言和QT实现可视化的图形监控和管理工具。     

Using interpreted CompositeCalls to improve operating system services

A large number of protection domain crossings and context switches is often the cause of bad performance in complex object‐oriented systems. We have identified the CompositeCall pattern which has been used to address this problem for decades. The pattern modifies the traditional client/server interaction model so that clients are able to build compound requests that are evaluated in the server domain. We implemented CompositeCalls for both a traditional OS, Linux, and an experimental object‐oriented μkernel, Off++ . In the first case, we learned about implications of applying CompositeCall to a non‐object‐oriented ‘legacy’ system. In both experiments, we learned when CompositeCalls help improving system performance and when they do not help. In addition, our experiments gave us important insights about some pernicious design traditions extensively used in OS construction. Copyright © 2000 John Wiley & Sons, Ltd.     

一种基于Linux的网络数据库设计方案

介绍了网络数据库的一些应用问题 ,并讨论了一种基于Linux和Java的网络数据库的实现方法。该方案用MySQL实现服务器端的网络数据库 ,用Java实现客户端与服务器的连接 ,具有良好的跨平台效果     

Parallel computation with dynamic load distribution for locally distributed Windows NT environments

Today 's requirements for computational power are still not satisfied. One answer for this demand is expensive supercomputers. Another attempt is the collection of computational power in a network. Connected workstations operate for parallel computation. Our approach for collecting unused resources in workstation clusters enables dynamic distribution of computational load over the network. Any computer individually distinguishes the amount of server resources sharing for others in the network. Our architecture is based on the client /server model —clients divide potentially hard problems into sub problems and forward them to different servers in the network. The usage of standardized remote procedure calls (rpc) as the basic mechanism for transmission of data between the workstations allows the extension of the concept for heterogeneous environments. This article gives a discussion of our implementation for Windows NT and presents the latest benchmarks with two special parallel applications.     

基于嵌入式Linux的网络视频监控系统

介绍一种网络视频监控系统实现方案,系统以嵌入式Linux和嵌入式微控制器S3C2410为核心平台,通过嵌入式平台建立的Web服务器将USB摄像头采集来的视频信号,经过网络传输,完成对测控现场和测试设备的网络视频监控任务.详细介绍了在上述嵌入式平台上USB设备的驱动开发以及如何在嵌入式Linux下实现视频采集,并完成了在该嵌入式平台上的应用程序的移植.     

NFS-CD: Write-Enabled Cooperative Caching in NFS

We present the network file system with cluster delegation (NFS-CD), an enhancement to the NFSv4 that reduces server load and increases the scalability of distributed file systems in computing clusters. The cluster delegation feature of NFS-CD allows data sharing among clients by extending the NFSv4 delegation model so that multiple clients manage a single file without interacting with the server. Based on cluster delegation, we implement a fast-commit primitive, cooperative caching, and the ability to recover the uncommitted updates of a failed computer. NFS-CD supports both read and write operations in the cooperative cache without degrading the consistency model of NFSv4. We have implemented NFS-CD by modifying the Linux NFSv4 client only. Because the server remains unchanged, NFS-CD preserves the simple administration model of NFSv4 and interoperates with standard NFS clients. NFS-CD offers improved performance when compared to NFSv4 at the expense of slightly weaker reliability guarantees. An experimental evaluation of our implementation, using industry standard benchmarks and application workloads, reveals that NFS-CD reduces server load by more than half. It also demonstrates that under most workloads, file systems must support writes to the cooperative cache to achieve scale.     

OPC跨平台通信的实现方法

随着工业自动化的发展,工控领域中常常会遇到异构平台之间的用于过程控制的OLE（oPc）通信问题。提出3种方法,分别利用EntireX DCOM,Java以及XMLOPC,在Linux下开发OPC客户端。使用Linux上的OPC客户端访问Windows平台上的OPC服务器,从而实现OPC的跨平台通信。描述各种方法的关键技术并给出相关代码,并对所有实现方法进行比较,分析它们在工业应用中的前景。     

Linux集群实时监控系统的一种实现方法

随着云计算技术的日益发展, Linux集群以造价低廉、易于扩充等优势得到了愈来愈广泛的应用. 为了更好地发挥集群性能, 充分利用集群节点的资源, 对集群性能进行实时监控是很有必要的. 提出了一种Linux集群监控器设计与实现方法. 该方法通过每隔一段时间采集节点机/proc虚拟文件系统中的信息, 如CPU和内存使用情况等. 经过过滤后, 通过socket传输给监控服务器. 论文首先给出了监控器的总体设计方案, 整个监控系统由守护在管理节点上的信息管理服务器进程和运行在各个计算节点上的采集器进程组成. 然后分采集器和信息管理器两大部分, 分别介绍了其具体的设计框架和其采用的关键技术. 采集器分主要由信息采集、信息处理和信息传送3 个模块组成, 分别采用3 个线程来完成. 信息管理器采用了线程池技术, 用以接受采集器发送过来的传输请求. 实践证明, 该系统可以很好地满足实时监控Linux 集群性能的需要.     

Linux高性能计算集群的设计与实现

计算机和网络硬件设备逐步实现商品化和标准化,PC机或工作站的性能越来越高而价格越来越便宜,同时开源Linux微内核及集群工具中间件技术也日趋成熟稳定,高性能计算集群逐渐发展起来,并成为主流的高性能计算平台。高性能计算集群逐渐替代专用、昂贵的超级计算机对大规模并行应用构建原型、调试和运行。基于PCs或工作站的高性能计算快速部署及其可靠性和可管理性研究,对高性能计算集群在科学研究和工程计算等领域的应用,促进高性能计算技术的应用方面具有深远的意义。本文以OSCAR集群为实例,部署一个五结点的集群环境并运行简单的并行测试例子。     

A distributed implementation of a virtual machine for Java

The cluster virtual machine (VM) for Java provides a single system image of a traditional Java Virtual Machine (JVM) while executing in a distributed fashion on the nodes of a cluster. The cluster VM for Java virtualizes the cluster, supporting any pure Java application without requiring that application be tailored specifically for it. The aim of our cluster VM is to obtain improved scalability for a class of Java Server Applications by distributing the application's work among the cluster's computing resources. The implementation of the cluster VM for Java is based on a novel object model which distinguishes between an application's view of an object (e.g. every object is a unique data structure) and its implementation (e.g. objects may have consistent replications on different nodes). This enables us to exploit knowledge on the use of individual objects to improve performance (e.g. using object replications to increase locality of access to objects). We have already completed a prototype that runs pure Java applications on a cluster of NT workstations connected by a Myrinet fast switch. The prototype provides a single system image to applications, distributing the application's threads and objects over the cluster. We used the cluster VM to run, without change, a real Java Server Application containing over 10 Kloc

1 Kloc means Kilo lines of code—used to describe the size of applications in terms of source lines count.

for the source code and achieved high scalability for it on a cluster. We also achieved linear speedup for another application with a large number of independent threads. This paper discusses the architecture and implementation of the cluster VM. It focuses on achieving a single system image for a traditional JVM on a cluster while describing, in short, how we aim to obtain scalability. Copyright © 2001 John Wiley & Sons, Ltd.     

Parallel bisecting <Emphasis Type="Italic">k</Emphasis>-means with prediction clustering algorithm

In this paper, we propose a new parallel clustering algorithm, named Parallel Bisecting k-means with Prediction (PBKP), for message-passing multiprocessor systems. Bisecting k-means tends to produce clusters of similar sizes, and according to our experiments, it produces clusters with smaller entropy (i.e., purer clusters) than k-means does. Our PBKP algorithm fully exploits the data-parallelism of the bisecting k-means algorithm, and adopts a prediction step to balance the workloads of multiple processors to achieve a high speedup. We implemented PBKP on a cluster of Linux workstations and analyzed its performance. Our experimental results show that the speedup of PBKP is linear with the number of processors and the number of data points. Moreover, PBKP scales up better than the parallel k-means with respect to the dimension and the desired number of clusters. This research was supported in part by AFRL/Wright Brothers Institute (WBI).     

Java Servlet模式的WebGIS性能优化研究*

探讨了使用Java Servlet模式实现WebGIS的优势与方法,采用GeoServer与OpenLayers结合的方式设计并实现了一种Java Servlet模式的WebGIS系统.由于服务器端性能的优劣直接影响到客户端用户的使用和体验效果,因此对WebGIS服务器端性能问题进行了深入研究,提出了JVM(Java虚...     

基于改进心跳包机制的整流远程监控系统

为了保持基于TCP/IP协议的远程通信的快速性和稳定性,设计一种基于Socket的心跳包机制,并将其应用于一个基于C/S模式的远程监控系统。在客户机与服务器两端设计不同的心跳机制,通过在服务器与客户机之间传递心跳包数据,判断服务器与客户机之间的连接状况,并在网络堵塞时通过连续请求连接来实现重新连通,从而保证系统在网络堵塞时能够有效连通,在网络断开时提示用户。在一个单服务器多客户机模式的模型下,用Socket实现了该机制。该心跳包机制已应用于一个C/S模式的整流装置远程监控系统,通过对系统和模型进行测试表明,该模型达到了较好的效果,提升了系统的可用性和可靠性。     

A concurrent process creation service to support SPMD based parallel processing on COWs

Current software environments used to support parallel processing on a cluster of workstations (COW) are not satisfactory, do not provide complete transparency and are not specifically designed for parallel processing. In particular, the establishment of a parallel processing environment and the initialisation of parallel processes suffer from poor performance. Each parallel process of an application is created sequentially and in many cases the logon operation must be completed before remote resources could be acquired. These operations are also performed manually. We present in this paper an original approach that addresses the problem of parallel process creation. The remote workstations are acquired completely transparently and dynamically, and parallel processes are created concurrently. To demonstrate the feasibility of this approach we show a system based on RHODOS (a client/server and microkernel based distributed operating system), specifically designed to improve the performance of process instantiation and therefore able to improve the overall execution performance of parallel programs, in particular parallel process creation. Copyright © 1999 John Wiley & Sons, Ltd.