一种改进的自适应页面置换算法

研究缓冲区页面置换策略和算法(特别是自适应页面置换策略和算法),提出一种基于双管理链的自适应页面置换算法HA。HA算法是对DMC(2c)算法的改进,它引入动态置换点,同时,根据缺页失败数确定算法的工作链,并根据页面访问序列的局部特征选择效率较高的页面置换策略。实验结果表明,HA算法能有效地减少缺页失败数,降低缺页率,特别是在处理第三种模式的页面访问序列时,该算法的缺页率较改进前的算法可降低近30%。     

对页面访问序列影响LRU页面置换算法的研究

页面置换算法是操作系统中虚拟存储管理的一个重要部分。改进页面置换算法,可以降低页面失败率,从而有效地提高系统性能。现有的应用于虚拟存储管理的页面置换算法主要是Least Reference Used(LRU)页面置换算法。文中利用页面访问间隔数,分析不同的页面访问序列对LRU算法的影响,把页面访问序列分为LRU-友好页面访问序列、LRU-不友好页面访问序列、不友好页面访问序列三类,为改进LRU页面置换算法提供了依据。     

使用矩阵实现LRU的页面置换算法

操作系统的内存管理一直是计算机领域研究的一个重要方向。文中分析了几种常用内存管理中的页面置换算法及其存在的问题,提出了LUR页面置换算法的操作系统内存管理中比较接近理想算法的一种页面置换算法,并阐述了使用矩阵方法实现该页面置换算法的原理。     

对页面访问序列影响LRU页面置换算法的研究

页面置换算法是操作系统中虚拟存储管理的一个重要部分。改进页面置换算法，可以降低页面失败率，从而有效地提高系统性能。现有的应用于虚拟存储管理的页面置换算法主要是Least Reference Used（LRU）页面换算法。文中利用页面访问间隔数，分析不同的页面访问序列对LRU算法的影响，把页面访问序列分为LRU-友好页面访问序列、LRU-不友好页面访问序列、不友好页面访问序列三类，为改进LRU页面置换算法提供了依据。     

置换表示方法求解多卫星多地面站调度问题

针对多卫星成像和多地面站数传并存的对地成像调度问题,从置换空间到调度解空间的映射方法和置换空间的搜索算法两方面进行了研究.提出了一种数传时间窗优先的置换序列映射算法,并证明该映射算法可以将置换序列映射到调度解空间上的最优解.提出了一种遗传随机搜索算法,基于有记忆随机邻域搜索,在置换空间上进行搜索.仿真计算表明,随机邻域搜索可以增强遗传算法的局部搜索能力,搜索结果平均获得了4.64%的改进.     

基于BHO构建轻量级上网行为监控系统

基于BHO劫持技术实现了一个轻量级的上网行为监控系统.该系统通过BHO实现与IE浏览器的绑定,确保了用户每个Web页面浏览行为都能得到有效监控.通过捕获DISPID_BEFORENAVIGATE2和DISPID DOCUMENTCOMPLETE事件,并使用页面替换和脚本执行两种方式,实现了网站屏蔽和网页过滤功能,达到了对用户浏览不良或非法Web页面行为进行监控的目的.通过使用模块化设计思路和“捎带”的“心跳”信号报告策略,使得系统能够同时适用于个人用户和机构用户,并具有较高的通信效率,从而提供了一种具有较好通用性和有效性的网络防护手段.     

基于模板技术的产品大规模定制信息发布模型

提出了基于模板技术的产品定制信息发布模型,该模型根据产品定制系统页面输出样式,通过模板定义层定义页面输出模板,并由模板生成层生成并保存页面输出模板;系统输出数据通过页面输出发布程序,结合相应的页面输出模板生成Web发布页面。该模型实现了系统信息发布页面的灵活定制和信息输出发布软件的复用。     

基于条件随机域的垃圾信息特征复原

通过加入噪声、替代文字等手段隐藏信息内容的真实符号分布,是目前垃圾制造者干扰或躲避过滤器检测的主要手段。介绍一种使用基于条件随机域的序列方法实现垃圾信息特征复原的技术。该方法比现有的基于模式匹配、基于序列比对和基于隐马尔科夫模型等方法在模型建立上有着更大的灵活性和鲁棒性。实验表明,使用条件随机域的特征复原方法可以明显提高基于压缩和内容过滤器的过滤性能。     

基于探测的自适应页面置换算法研究

页面置换算法是虚拟存储管理的重要组成部分,页面置换算法的优劣将直接影响系统的整体性能。本文在分析传统页面置换算法存在不足的基础上,介绍一种能够弥补传统页面置换算法存在不足的基于探测的自适应页面置换算法,同时分忻了该算法的性能,并且指出了进一步的研究方向。     

Internet中WWW多层次缓冲模型的设计

针对当前ＷＷＷ服务速度越来越慢的情况,提出了ＷＷＷ服务的多层次缓冲结构模型,讨论了该缓冲模型中的页面置换算法问题和信息一致性问题,并给出了几种页面置换算法及其性能分析。     

Segmentation,paging and optimal page sizes in virtual memory

On the basis of empirical data two topics concerning virtual memory systems are discussed: determining an optimal page size and performance of segmentation as compared to paging. Several production programs have been executed (on a simulator) both in a segmented system and in a paged system with various page sizes; the memory management was based on the working set policy. The memory usage and the fault rates were recorded, and the lifetime functions and space-time integrals were evaluated. The observations are explained using a new model of program behaviour which is a refinement of the phase-transition model. The results show that there is no globally optimal page size. Two characteristic types of programs are observed: the first requires a small page size and a large window size, the second requires a large page size and a small window size. Segmentation and paging are compared with respect to their usage of various resources. In the sense of the space-time integral, segmentation usually outperforms paging; if the mean segment size is large, the difference is remarkable. Several commonly used assumptions about the effects of page size on program behaviour are validated; some of them are found inaccurate or even wrong.     

ASP.NET中实现数据分页的几种方法

ASP.NET是一种服务器端制作动态WEB页的全新编程手段。该文讨论了在ASP.NET框架下对WEB数据库几种实现分页显示的方法。对利用自带分页功能的数据控件(如:DataGrid)和对于没有自带分页功能的控件(如:DataList)进行分页分别结合实例进行了详细的阐述。     

Zur Verbesserung der Lokalität im Zugriff auf Felder

In the literature the reduction of the page fault rate in a paging environment is oriented towards the analysis of reference strings of program addresses. Here we describe a method to improve the locality property in referencing data areas, which we discuss in the actually interesting case of accessing arrays. If the programmer has a suited tool in his programming language to express the freedom in the reference sequence on data, then the compiler can fix the sequence as to minimize the paging behaviour. The details of this approach are given.     

A Unified Analysis of Paging and Caching

Paging (caching) is the problem of managing a two-level memory hierarchy in order to minimize the time required to process a sequence of memory accesses. In order to measure this quantity, which we refer to as the total memory access time, we define the system parameter miss penalty to represent the extra time required to access slow memory. We also introduce the system parameter page size. In the context of paging, miss penalty is quite large, so most previous studies of on-line paging have implicitly set miss penalty =∞ in order to simplify the model. We show that this seemingly insignificant simplification substantially alters the precision of derived results. For example, previous studies have essentially ignored page size. Consequently, we reintroduce the miss penalty and page size parameters to the paging problem and present a more accurate analysis of on-line paging (and caching). We validate using this more accurate model by deriving intuitively appealing results for the paging problem which cannot be derived using the simplified model. First, we present a natural, quantifiable definition of the amount of locality of reference in any access sequence. We also point out that the amount of locality of reference in an access sequence should depend on page size among other factors. We then show that deterministic and randomized marking algorithms such as the popular least recently used (LRU) algorithm achieve constant competitive ratios when processing typical access sequences which exhibit significant locality of reference; this represents the first competitive analysis result which (partially) explains why LRU performs as well as it is observed to in practice. Next, we show that finite lookahead can be used to obtain algorithms with improved competitive ratios. In particular, we prove that modified marking algorithms with sufficient lookahead achieve competitive ratios of 2. This is in stark contrast to the simplified model where lookahead cannot be used to obtain algorithms with improved competitive ratios. We conclude by using competitive analysis to evaluate the benefits of increasing associativity in caches. We accomplish this by specifying an algorithm and varying the system configuration rather than the usual process of specifying the system configuration and varying the algorithm. Received August 7, 1995; revised May 7, 1996, and August 6, 1996.     

基于影子页面和混合日志的MMDB恢复方法

为了提升内存数据库从各种故障中恢复的速度,提出了基于影子页面技术、混合日志策略以及模糊检查点思想的内存数据库恢复方法。在分析内存数据库运行过程中主要的时间消耗点的基础上建立了内存数据库的系统模型,通过分析事务过程和检查点过程,讨论了该恢复策略的执行过程以及优点,讲述了内存数据库在此系统模型和恢复策略下的事务故障和系统故障的恢复过程以及系统的性能分析。     

A multiclass network model of a demand paging computer system

Summary The paper presents a multiclass network model of a demand paging computer system. The powerful class and class changing mechanism of a multiclass network are used to model the serial co-operation of user and system functions in program execution. The workload itself is modelled as a mix of programs, each with different CPU, I/O, paging and locality characteristics. The effect of paging, I/O and program termination overheads on systems performance is evaluated, as well as the transient overhead of rapid page loading upon program activation. The model is then used to compute the optimal multiprogramming level and the optimal multiprogramming mix as a function of workload composition and system overhead. The model is finally used to confirm certain heuristic load control rules proposed by Denning et al.     

基于分页缓存模型的用户兴趣跟踪方法

对智能推荐系统中用户兴趣跟踪问题的研究,传统方法如时间窗口、遗忘函数等在表征用户兴趣模型时均未考虑兴趣主题概念相关性,无法充分利用用户历史数据,导致兴趣跟踪不准确。因此,本文提出了基于分页缓存的用户兴趣表征模型,形成基于主题的用户多兴趣域结构,并提出了相应的兴趣迁移检测SIM算法,该算法引入序列熵差,表征兴趣迁移的整体特性。实验表明,与传统方法相比,本文提出的方法具有更低的兴趣平均绝对偏差,能够更准确地表征用户兴趣迁移,从而获得更好的推荐质量和效率。     

低轨卫星通信网络中动态位置更新管理方案

移动性管理是LEO(低轨卫星(low earth orbit))卫星网络通信系统中的一个重要问题.提出了LEO网络中一种改进的基于移动的位置更新和寻呼方案.在这种方法中我们引入了"元小区"概念,它由两个相邻波束组成.首先阐述了基于"元小区"模型的位置管理策略,然后推导了基于移动的动态位置管理的数学模型,并利用该模型分别计算了LEO网络中单位呼叫的位置更新和寻呼代价.通过元小区方案和普通小区的在各种网络参数环境下的性能比较证明了"元小区"方法的有效性和健壮性.最后为了进一步减小"元小区"方法中的寻呼代价,提出了强制更新策略,它强制移动终端在穿越两颗卫星覆盖区的边界时进行位置更新操作.     

Web应用程序分页策略的研究

研究了在Web应用程序中被广泛使用的分页技术,介绍了3种常用的分页模型,利用计算页面被访问的概率密度的方法对这3种分页模型进行了分析。在此基础上讨论了动态建它合适的分页策略的方法。将该方法应用于实际系统的分页框架中,取得了良好效果。该框架可以灵活地定制不同的分页策略。     

基于Ajax的大量数据动态浏览的实现方法研究

针对传统Web应用对批量数据显示采取分页技术在页面切换过程中存在用户等待时间长的突出问题,提出了基于Ajax平台的异步传输方法,并详细讨论了基于Ajax的拖拽表格的设计方法,最后在基金支持项目高校组织人事管理信息系统上得到成功应用。结果发现使用拖拽表格显示大量数据有效减少了用户交互过程中的等待时间,提高了系统的响应速度。同时由于客户端分担部分业务层逻辑,从而减轻了服务器压力。