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下一代网络业务提供是一个分布式系统,在支持通信类增值业务时要求一定的QoS保证。实时CORBA采用面向对象的方法,提高了分布式应用软件的可重用性和可扩展性,大大简化了分布式应用系统的开发和维护,便于异构环境下的系统集成;而且为分布实时应用提供端到端的可预测性。结合实时CORBA规范及其产品中的实现技术,讨论了实时CORBA的资源控制策略及其实现的协议框架,并用试验分析验证它的实时性能。实时CORBA改善了通用CORBA的实时性能,能够为下一代网络业务提供一定的实时保证。 相似文献
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下一代网络业务提供是一个分布式系统,在支持通信类增值业务时要求一定的QoS保证。实时CORBA采用面向对象的方法,提高了分布式应用软件的可重用性利可扩展性,大大简化了分布式应用系统的开发和维护,便于异构环境下的系统集成;而日.为分布实时应用提供端到端的可预测性。结合实时CORBA规范及其产品中的实现技术,讨论了实时CORBA的资源控制策略及其实现的协议框架,并用试验分析验证它的实时性能。实时CORBA改善了通用CORBA的实时性能,能够为下一代网络业务提供一定的实时保证。 相似文献
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用线程池解决服务器并发请求的方案设计 总被引:6,自引:0,他引:6
许多实际应用要求服务器具有同时为多个客户提供服务的能力,开发一个性能优良的服务器程序,就必须同时接收并处理多个客户连接,并对每个客户提供快速响应。用多线程来同时为多个客户提供服务,用线程池技术可以高效地处理网络通信中服务器的并发请求。描述了线程池处理服务器并发请求的设计方案,给出了用线程池技术实现的邮件服务器实例,并对线程池技术做了具体的分析。 相似文献
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随着基于Internet技术的电子商务的普及,传统的ClientPServer二层体系结构不再适应更为复杂和灵活的大规模商业应用的需求,逐渐被三层甚至多层体系结构所代替,其中,采用应用服务器作为中间件的三层体系结构在电子商务系统中得到了较为广泛的应用.本文主要讨论了使用目前比较流行的CORBA中间件技术和WebLogic应用平台以及EJB处理业务的能力,设计实现一个支持Web分布式应用的电子商务系统的方法. 相似文献
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本文根据硬件线程的特征,为硬件线程调度建立了一个周期与非周期混合线程集的调度模型.在数学层面描述了硬件多线程调度中每个线程被成功调度的条件判据.并在此基础之上,提出一种以截止时间与最坏执行时间差为基本因子的DR-EDF算法,提供了一种实现这种DR-EDF算法的硬件多线程控制器的设计原理.最后用FPGA为载体,实现了一款硬件多线程处理器,通过实际测试的分析结果,得出这种面向硬件多线程的实时调度算法在不影响线程集错失率前提下,提高了嵌入式系统中紧急任务的可调度性. 相似文献
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服务器的并发控制策略是对服务器性能评估的基本要求.它可以提高系统的并发控制能力以及改善交互响应时间.采用恰当的技术实现服务器的并发处理请求,是成功制定服务器并发控制策略的关键.Windows网络服务提供的并发控制技术有多种,它们大都是基于线程并发结构.在这些技术中,线程池和完成端口应用较为广泛并颇受好评.这里从线程池技术和完成端口技术两方面着手,介绍如何处理网络通信中服务器的并发请求.并给出不同需求的服务器应该采用何种处理技术. 相似文献
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提出一个以信息调度为基础的分布式的QoS(DQBI)体系结构。该结构可以在移动Ad Hoc网络中为实时传输和尽力而为传输提供QoS保证。DQBI模型改进了整个系统信息端到端的延迟性能,并且通过使用请求允许接入控制和拥塞控制机制来处理网络的拥塞。最后,仿真比较了MQRD结构和DQBI结构,发现DQBI结构可以更好地确保实时流和尽力而为流实现它们期望的服务水平。 相似文献
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可扩展的并行计算机正广泛地应用于需要高性能、高可靠性的应用领域,集群并行计算机的诞生被誉为并行计算机工业的一次革命,它重新定义了超级计算机的概念.基于中间件技术提出一种新的动态实时集群体系结构(RTCC),定义了实时集群的相关组件和协议,并详尽地阐述了实时集群系统的设计和实现. 相似文献
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Techniques for enhancing real-time CORBA quality of service 总被引:5,自引:0,他引:5
Pyarali I. Schmidt D.C. Cytron R.K. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》2003,91(7):1070-1085
End-to-end predictability of remote operations is essential for many fixed-priority distributed real-time and embedded (DRE) applications, such as command and control systems, manufacturing process control systems, large-scale distributed interactive simulations, and testbeam data acquisition systems. To enhance predictability, the Real-time CORBA specification defines standard middleware features that allow applications to allocate, schedule, and control key CPU, memory, and networking resources necessary to ensure end-to-end quality of service support. This paper provides two contributions to the study of Real-time CORBA middleware for DRE applications. First, we identify potential problems with ensuring predictable behavior in conventional middleware by examining the end-to-end critical code path of a remote invocation and identifying sources of unbounded priority inversions. Experimental results then illustrate how the problems we identify can yield unpredictable behavior in conventional middleware platforms. Second, we present design techniques for ensuring real-time quality of service in middleware. We show how middleware can be redesigned to use nonmultiplexed resources to eliminate sources of unbounded priority inversion. The empirical results in this paper are conducted using TAO, which is widely used and open-source DRE middleware compliant with the Real-time CORBA specification. 相似文献
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数据分发服务DDS是面向分布式实时系统的中间件技术规范。随着分布式实时系统复杂度和规模的增大,系统对数据传输的质量要求也在大幅提高。DDS采用以数据为中心的发布/订阅模式,能够有效满足各种分布式应用的性能要求和硬实时要求。文中围绕数据分发服务技术展开讨论,分析对比了4种常见的数据分发模型,指出了各自的优缺点。文中围绕通信机制、服务质量、传输框架、发现过程以及标准实现等5个方面对DDS规范进行了阐述;从DDS配置的复杂性、广域网应用DDS以及无线网络应用DDS共3个方面重点介绍了DDS应用面临的挑战,并探讨了未来的研究方向。 相似文献
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Gill C.D. Cytron R.K. Schmidt D.C. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》2003,91(1):183-197
Increasingly complex requirements, coupled with tighter economic and organizational constraints, are making it hard to build complex distributed real-time embedded (DRE) systems entirely from scratch. Therefore, the proportion of DRE systems made up of commercial-off-the-shelf (COTS) hardware and software is increasing significantly. There are relatively few systematic empirical studies, however, that illustrate how suitable COTS-based hardware and software have become for mission-critical DRE systems. This paper provides the following contributions to the study of real-time quality-of-service (QoS) assurance and performance in COTS-based DRE systems: it presents evidence that flexible configuration of COTS middleware mechanisms, and the operating system (OS) settings they use, allows DRE systems to meet critical QoS requirements over a wider range of load and jitter conditions than statically configured systems; it shows that in addition to making critical QoS assurances, noncritical QoS performance can be improved through flexible support for alternative scheduling strategies; and it presents an empirical study of three canonical scheduling strategies; specifically the conditions that predict success of a strategy for a production-quality DRE avionics mission computing system. Our results show that applying a flexible scheduling framework to COTS hardware, OSs, and middleware improves real-time QoS assurance and performance for mission-critical DRE systems. 相似文献
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由于数据分发服务(DDS)一方面定义了以数据为中心的发布/订阅模型,允许应用程序实时地发布信息,并订阅所需要的信息;另一方面还提供了异步、松耦合、实时可靠数据分发服务质量(QoS)服务。所以,DDS 适用于性能要求高、可预见性强的军用实时关键任务领域。文中针对全国产化 DDS 产品ZRDDS,从处理器、操作系统、通信方式的差异性屏蔽 方法给出了跨平台实现策略,并以国产化华睿 2 号处理平台为例,对关键路径进行瓶颈分析,找出优化点,同时针对硬件 平台的特性给出优化方法。文中所述技术具有普适性,适用于各类通信中间件的设计,优化后的通信中间件 ZRDDS 可广泛应用于各类军用即时分布式系统。 相似文献
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Mobile computing environments are characterized by heterogeneity—systems consisting of different device types, operating systems, network interfaces, and communication protocols. In a realistic scenario of context-aware computing, we should be able to deploy context management middleware throughout the distributed system at every device, despite its resource limitations, and the developer should be able to evolve the context model whenever new context-aware applications or context providers are introduced. This article presents a middleware architecture and design strategies that address these requirements without compromising efficiency. 相似文献
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Peer-to-peer systems that dynamically organize, interact and share resources are increasingly being deployed in large-scale environments. The location, intermittent connectivity, and organization of the peers have significant impact on meeting the quality of service requirements of distributed applications. This article presents the design, implementation, and empirical evaluation of a middleware architecture for managing distributed objects in peer-to-peer systems. The architecture consists of a self-organizing infrastructure that uses only local knowledge to dynamically form overlays of multiple peers and respond to changing processing and networking conditions; and a management layer that monitors the behavior of the applications transparently, schedules object invocations over multiple machines, and obtains accurate resource projections. The system works in a two-level feedback loop structure that uses measurements of elapsed time and resource loads to refine the initial estimates and revise the peer connections. Our empirical evaluation shows that the system manipulates the peer connections dynamically in response to changes in resource utilization to meet application end-to-end soft real-time requirements. 相似文献
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Experience demonstrates the benefits and feasibility of supporting multimedia applications in distributed middleware architectures. However, deployment of multimedia-capable middleware platforms has not yet occurred on a large scale. This article describes designing such a platform and its attempts to maximize performance, predictability, and configurability in a standard workstation operating system environment 相似文献