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基于排队网络的容量分析与模拟 总被引:2,自引:1,他引:2
客户机/服务器模型(Client/Server)是当前计算机网络系统应用最广泛的模型。为了提高系统的服务等级(Degree of Servier),找到制约系统性能的瓶颈,对系统进行分析以及模拟就显得十分的重要。基于排队网络建立了客户机/服务器模型。介绍了排队网络的MVA算法,并提出了一个近似的算法。并且,结合一个实例介绍了如何进行系统性能分析;最后,用离散事件模拟工具(Discrete Events Simulation Tool)OMNET进行了模拟,验证了分析的可靠性。 相似文献
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基于排队网络的容量分析与模拟 总被引:1,自引:0,他引:1
客户机服务器模型是当前计算机网络系统应用最广泛的模型。为了提高系统的服务等级,找到制约系统性能的瓶颈,对系统进行分析以及模拟十分重要。本文基于排队网络建立了客户机服务器模型;介绍了排队网络的MAV算法并提出一个近似算法;结合一个实例介绍了如何进行系统性能分析;最后,用离散事件模拟工具OMNET进行模拟,验证了分析的可靠性。 相似文献
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通过介绍Linux服务器系统的安全扫描工具,从Linux服务器系统漏洞分析与防护、安全检查与分析两个方面对Linux服务器系统进行安全风险分析,提出加强Linux服务器用户及文件系统管理,在操作系统层面对Linux服务器系统进行安全防护。安全扫描作为有效的自我检查改进途径,能及时发现现有防御手段的不足和新的漏洞隐患,指导做好系统漏洞的修复和加固,有针对性地定期安全检查可以避免因配置和权限控制不当、未执行有效的自我安全检查造成安全事件的发生,确保业务数据的连续性,减少数据被篡改或者数据丢失的风险,增强服务器系统的安全防护能力。 相似文献
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该文提出经工过程仿真训练系统的单元过程多模型集成方法,用有限状态自动机控制的集成多模型描述方法,描述了经工过程仿真系统的单元过程模型,进而讨论了对集成的多模型进行仿真的方法,提出了状态转换的监测与协调算法。把引发状态转换的事件分析为四类:数据通讯,教师台操作高等系统事件,外部操作,发生时间可预先确定的显式事件;由工艺参数和/或控制信号的变化引发的,发生时间不能预先定的隐式事件,分别讨论了多各事件在 相似文献
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离散事件系统的监控器可以通过禁止可控事件来使系统满足安全性和活性规范。然而,监控器并不对允许发生的可控事件主动进行选择,所以存在同时允许多个可控事件发生的情况。但在实际应用中,如交通调度、机器人路径规划中,要求系统在每个状态下最多只允许一个可控事件的发生。针对上述问题,引入一种最优机制来量化控制成本,并提出一种离散事件系统最优监督控制算法,以确保系统的安全性和活性,并使事件执行累计的成本最小。首先,给定受控系统和行为约束的自动机模型,并基于Ramadge和Wonham的监督控制理论求解出无阻塞和行为最大许可的监控器;其次,通过定义的成本函数为监控器中每个事件的执行赋予相应成本;最后,利用动态规划思想迭代计算求解出最优定向监控器,从而实现每个状态下最多发生一个可控事件和事件执行累计的成本最小的目标。使用单向列车导轨案例和多轨道列车控制案例来验证所提算法的有效性和正确性。对于上述两个案例,所提算法求解的定向监控器到达目标状态所需的事件执行累计的成本分别为26.0和14.0,低于贪心算法的27.5和16.0,以及Q-learning算法的26.5和14.0。 相似文献
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分布式数据流处理系统的动态负载平衡技术 总被引:4,自引:0,他引:4
设计了一种新的大规模分布式数据流处理系统的体系结构。系统由一组异构的服务器集群组成,负载在每个服务器集群内部多台同构的服务器之间获得平衡,从而达到整个系统的负载平衡。集群设计的主要目标之一是以资源换性能,服务器集群中服务器的最大数目足够保证系统不再发生过载现象,不再需要会降低性能的卸载技术。而且投入运行的服务器的数目根据实际的系统负载来决定,负载较轻时,一部分服务器可以进入休眠状态来减少能源的消耗。根据系统动态增减服务器的特点,设计了全新的初始化算法、动态负载平衡算法。与以前的分布式数据流处理系统相比,由于单个集群的服务器的数目大大减少,算法复杂性降低、速度加快、优化的空间增大。 相似文献
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并行视频服务器调度算法研究 总被引:3,自引:0,他引:3
从服务器缓冲要求,客户端缓冲要求,系统响应时间三个方面着重分析比较了在服务器推动模型基础上建立的两种调度算法,并发推动调度算法和改进的并发推动调度算法,为我们进行相关的系统设计提供了理论依据. 相似文献
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在计及客户的等待时间的前提下,配置多级多服务器队列系统参数从而最大化效益。给出单级多服务器系统和多级多服务器队列系统等待时间的概率分布函数,构建在截止期限约束下的效益最大化模型,并通过启发式算法来寻找最优解。数值模拟结果表明所得最优方案在实现最大化效益的同时,能够有效减少客户等待时间。 相似文献
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从用户角度远程探测代理服务器的通信特性。对代理的功能及分类进行总结,提出了代理服务器工作模型,对其逻辑模块和影响通信的因素进行分析。在此基础上分析代理特性探测原理,以HTTP代理为例设计了探测算法并实现了探测系统原型。该系统实现了Windows域环境下特定认证机制的穿透;经过测试并分析其性能,具有一定的适用性。 相似文献
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Service providers have begun to offer multimedia-on-demand services to residential estates by installing isolated, small-scale multimedia servers at individual estates. Such an arrangement allows the service providers to operate without relying on a highspeed, large-capacity metropolitan area network, which is still not available in many countries. Unfortunately, installing isolated servers can incur very high server costs, as each server requires spare bandwidth to cope with fluctuations in user demand. The authors explore the feasibility of linking up several small multimedia servers to a (limited-capacity) network, and allowing servers with idle retrieval bandwidth to help out servers that are temporarily overloaded; the goal is to minimize the waiting time for service to begin. We identify four characteristics of load sharing in a distributed multimedia system that differentiate it from load balancing in a conventional distributed system. We then introduce a GWQ load sharing algorithm that fits and exploits these characteristics; it puts all servers' pending requests in a global queue, from which a server with idle capacity obtains additional jobs. The performance of the algorithm is captured by an analytical model, which we validate through simulations. Both the analytical and simulation models show that the algorithm vastly reduces wait times at the servers. The analytical model also provides guidelines for capacity planning. Finally, we propose an enhanced GWQ+L algorithm that allows a server to reclaim active local requests that are being serviced remotely. Simulation experiments indicate that the scheduling decisions of GWQ+L are optimal, i.e., it enables the distributed servers to approximate the performance of a large centralized server 相似文献
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There are two problems with the privacy-preserving federal learning framework under an unreliable central server. ① A fixed weight, typically the size of each participant’s dataset, is used when aggregating distributed learning models on the central server. However, different participants have non-independent and homogeneously distributed data, then setting fixed aggregation weights would prevent the global model from achieving optimal utility. ②Existing frameworks are built on the assumption that the central server is honest, and do not consider the problem of data privacy leakage of participants due to the untrustworthiness of the central server. To address the above issues, based on the popular DP-FedAvg algorithm, a privacy-preserving federated learning DP-DFL algorithm for dynamic weight aggregation under a non-trusted central server was proposed which set a dynamic model aggregation weight. The proposed algorithm learned the model aggregation weight in federated learning directly from the data of different participants, and thus it is applicable to non-independent homogeneously distributed data environment. In addition, the privacy of model parameters was protected using noise in the local model privacy protection phase, which satisfied the untrustworthy central server setting and thus reduced the risk of privacy leakage in the upload of model parameters from local participants. Experiments on dataset CIFAR-10 demonstrate that the DP-DFL algorithm not only provides local privacy guarantees, but also achieves higher accuracy rates with an average accuracy improvement of 2.09% compared to the DP-FedAvg algorithm models. © 2022, Beijing Xintong Media Co., Ltd.. All rights reserved. 相似文献
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视频服务器的缓存管理对视频点播系统的性能有重要的影响。为了提高视频服务器的资源利用率、提高客户端节目的播放质量和流畅性,我们提出一种动态的缓存管理算法。该算法节省资源,有效地防止缓存上溢或下溢,为客户端的高质量播放提供可能。本文通过建立一个排队论模型对该算法进行分析,然后给出了详尽的算法描述,最后模拟仿真以证实其可行性和有效性。 相似文献
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朱强 《计算机工程与应用》2005,41(29):163-166
在分布式视频点播系统中,由于不同视频服务器到代理服务器之间的网络QoS状况可能存在较大的差异,因此多媒体代理服务器必须引入有效的服务器选择算法。文章主要讨论所提出的在多服务器模型下基于增益模型的服务器选择算法;通过仿真实验测试其性能、与其他算法进行比较;并分析此算法对环境参数变化的适应性。 相似文献
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Task scheduling in heterogeneous environments such as cloud data centers is considered to be an NP-complete problem. Efficient task scheduling will lead to balance the load on the virtual machines (VMs) thereby achieving effective resource utilization. Hence there is a need for a new scheduling framework to perform load balancing amid considering multiple quality of service (QoS) metrics such as makespan, response time, execution time, and task priority. Multi-core Web server is difficult to achieve dynamic balance in the process of remote dynamic request scheduling, so it is necessary to improve it based on the traditional scheduling algorithm to enhance the actual effect of the algorithm. This article do research on the multi-core Web server, Focusing on multi-core Web server queuing model. On this basis, the author draws the drawbacks of the multi-core Web server in the remote dynamic request scheduling algorithm, and improves the traditional algorithm with the demand analysis. Not only it overcomes the drawbacks of traditional algorithms, but also promotes the system threads carrying the same amount of tasks, and promotes the server being always in a dynamic balance. On the basis of this, it achieves an effective solution to customer requests. 相似文献
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