用双向链表来模拟数据库缓冲区

主要采用双向链表及LRU(最少页面使用置换)算法来模拟数据库缓冲区中页面的换入换出情况,统计了I0次数,命中页数等信息.可以学到双向链表的使用方法及其在插入删除操作过程中速度上的优势、LRU算法的实现过程、MFC中的列表等控件的使用方法等.     

一种基于闪存的缓冲区管理算法

在大多数以磁盘为存储系统的操作系统中,缓冲区管理算法只考虑到了数据访问的命中率。然而,闪存的写操作代价远远大于读操作代价。为了提高闪存性能,本文提出的O CFLRU（Optimal CFLRU）算法对于CFLRU（Clean First LRU）算法做了优化。该算法用一种页 块混合的数据结构来分别管理缓冲区中的干净页面和脏的数据页面聚簇。当缓冲区空间不够时,优先置换干净页面,再置换出脏的数据页聚簇,从而减少了写回的次数和随机写带来的擦除次数,提高了闪存的性能。     

Ubase数据库系统缓冲管理器的实现

缓冲区技术是减少系统对外存访问的重要方法之一。文章分析了Ubase数据库系统缓冲管理器的基本功能,对常用页面替换算法的性能进行了比较,最终选择Love/Hate算法代替LRU算法实现了Ubase数据库系统的缓冲管理,降低了系统的开销,提高了Ubase数据库系统的性能。     

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。     

一种对LRFU置换策略的自适应改进

数据库缓冲区页面置换算法对磁盘数据库的性能有着重要的影响,页面置换算法主要有基于访问时间的置换策略、基于访问次数的置换策略、两者结合的置换策略等。LRFU算法是一系列结合LRU和LFU置换策略的置换算法,很好地实现了两种置换策略的结合,但却没有给出一种在不同的应用场景中进行动态调整的机制。提出了一种对LRFU算法进行动态调整的方法,模拟测试发现改进的LRFU算法都不同程度地提高了缓冲区命中率。     

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。     

基于MGLRU的IP流统计算法

针对最近最久未使用(LRU)算法在高速网络中大流漏判率高的缺陷,提出一种基于多粒度最近最久未使用检测算法。该算法采用分层多粒度压缩计数机制对高速网络数据抽样,提高对长流的识别精度。基于实际的互联网数据进行仿真实验,结果表明,在给定条件下,该方法的内存占用量为LRU算法的50%,测量误差仅为LRU算法的10%。     

基于内容的代理服务器高速缓冲器研究

该文提出了一种新的加强代理服务器CACHE的技术。首先给出CHACE内容的标题层、逻辑层、物理层的三层模型。对其内容进行索引,以便比较、查询。并给出了考虑文件存储空间、访问时间的LRU算法,保证CACHE中内容总是最相关、使用率高的内容。提高了具有相同目的用户的访问效率。     

LRU算法的研究及实现

本文主要介绍页面置换算法中的LRU算法(leastrecentlyused),并将LRU算法与另外一些常用页面置换算法进行了比较。同时探讨了LRU算法的实现问题。     

面向对象数据库的缓冲区管理机制的设计与实现

缓冲区技术是减少系统对外存访问的重要方法之一。本文介绍了一面向对象数据库系统Ｏ＿２Ｓ的双缓冲区机制，阐述了页面缓冲区和对象缓冲区的管理数据结构及其缓冲区内的废品回收等。双缓冲机制能有效地提高应用对象的访问效率。     

Exploiting the least recently used page replacement algorithm

Many implementations of paged virtual memory systems employ demand fetching with least recently used (LRU) replacement. The stack characteristic of LRU replacement implies that a reference string which repeatedly accesses a number of pages in sequence will cause a page fault for each successive page referenced when the number of pages is greater than the number of page frames allocated to the program's LRU stack. In certain circumstances when the individual operations being performed on the referenced string are independent, or more precisely are commutative, the order of alternate page reference sequences can be reversed. This paper considers sequences which cannot be reversed and shows how placement of information on pages can achieve a similar effect if at least half the pages can be held in the LRU stack.     

Cold object identification in the Java virtual machine

Many Java applications instantiate objects within the Java heap that are persistent but seldom if ever referenced by the application. Examples include strings, such as error messages, and collections of value objects that are preloaded for fast access. This paper describes a stack‐based framework for detecting these ‘cold’ objects at runtime, with a view to marshaling and sequestering them in designated regions of the heap where they may be preferentially paged out to a backing store, thereby freeing physical memory pages for occupation by more active objects. Furthermore, we evaluate the correctness and efficiency of stack‐based approach with an access barrier. The experimental results from a series of SPECjvm2008 benchmarks are presented. Copyright © 2016 John Wiley & Sons, Ltd.     

Social Media as Information Source: Recency of Updates and Credibility of Information

Social media are increasingly being used as an information source, including information related to risks and crises. The current study examines how pieces of information available in social media impact perceptions of source credibility. Specifically, participants in the study were asked to view 1 of 3 mock Twitter.com pages that varied the recency with which tweets were posted and then to report on their perceived source credibility of the page owner. Data indicate that recency of tweets impacts source credibility; however, this relationship is mediated by cognitive elaboration. These data suggest many implications for theory and application, both in computer‐mediated communication and crisis communication. These implications are discussed, along with limitations of the current study and directions for future research.     

Recursion Engineering for Reduction Incorporated Parsers

Reduction Incorporated (RI) recognisers and parsers deliver high performance by suppressing the stack activity except for those rules that generate fully embedded recursion. Automaton constructions for RI parsing have been presented by Aycock and Horspool [John Aycock and Nigel Horspool. Faster generalised LR parsing. In Compiler Construction, 8th Intnl. Conf, CC'99, volume 1575 of Lecture Notes in Computer Science, pages 32 – 46. Springer-Verlag, 1999] and by Scott and Johnstone [Adrian Johnstone and Elizabeth Scott. Generalised regular parsers. In Gorel Hedin, editor, Compiler Construction, 12th Intnl. Conf, CC'03, volume 2622 of Lecture Notes in Computer Science, pages 232–246. Springer-Verlag, Berlin, 2003] but both can yield very large tables. An unusual aspect of the RI automaton is that the degree of stack activity suppression can be varied in a fine-grained way, and this provides a large family of potential RI automata for real programming languages, some of which have manageable table size but still show high performance. We give examples drawn from ANSI-C, Cobol and Pascal; discuss some heuristics for guiding manual specification of stack activity suppression; and describe work in progress on the automatic construction of RI automata using profiling information gathered from running parsers: in this way we propose to optimise our parsers' table size against performance on actual parsing tasks.     

基于STM32和LwIP协议栈的Web网页控制系统的设计与实现

为了降低基于嵌入式的Web网页智能家居控制系统的开发成本和整体系统的开发难度,介绍了以STM32单片机作为处理器,ENC28J60作为以太网通信芯片,在不使用操作系统的情况下,基于LwIP协议栈的Web网页智能家居控制系统的软、硬件的设计与实现.该方案不仅降低了开发成本,而且经过实际测验表明该方案性能可靠,使用方便,具有较高的应用价值.     

Minimization of demand paging for the LRU stack model of program behavior

The minimization of page faults in a demand paging environment where program behavior is described by the LRU stack model is studied. Previous work on this subject considered a specific type of stack probability distribution. As there exist practical situations which do not satisfy this assumption, we extend the analysis to arbitrary distributions. The minimization is stated as an optimization problem under constraints, a method to obtain a class of optimal solution is presented, and a fixed-space replacement algorithm to implement these solutions is proposed. The parameters of this replacement algorithm can be varied to adapt to specific stack probability distributions and to the number of allocated pages in memory. This paper also determines a necessary and sufficient condition for the optimality of the LRU algorithm.     

针对小文本的Web数据挖掘技术及其应用

现有搜索引擎技术返回给用户的信息太多太杂,为此提出一种针对小文本的基于近似网页聚类算法的Web文本数据挖掘技术,该技术根据用户的兴趣程度形成词汇库,利用模糊聚类方法获得分词词典组,采用MD5算法去除重复页面,采用近似网页聚类算法对剩余页面聚类,并用马尔可夫Web序列挖掘算法对聚类结果排序,从而提供用户感兴趣的网页簇序列,使用户可以迅速找到感兴趣的页面。实验证明该算法在保证查全率和查准率的基础上大大提高了搜索效率。由于是针对小文本的数据挖掘,所研究的算法时间和空间复杂度都不高,因此有望成为一种实用、有效的信息检索技术。     

面向信息检索需要的网络数据清理研究

Web数据中的质量参差不齐、可信度不高以及冗余现象造成了网络信息检索工具存储和运算资源的极大浪费,并直接影响着检索性能的提高。现有的网络数据清理方式并非专门针对网络信息检索的需要,因而存在着较大不足。本文根据对检索用户的查询行为分析,提出了一种利用查询无关特征分析和先验知识学习的方法计算页面成为检索结果页面的概率,从而进行网络数据清理的算法。基于文本信息检索会议标准测试平台的实验结果证明,此算法可以在保留近95%检索结果页面的基础上清理占语料库页面总数45%以上的低质量页面,这意味着使用更少的存储和运算资源获取更高的检索性能将成为可能。     

嵌入式网络中WEB SERVER的实现

本文介绍了在存储空间有限的嵌入式网络应用中，通过合理选择TCP／IP协议子集．将TCP／IP协议栈嵌入到一种增强型单片机P89C51RD2中．借助网卡芯片RTL8019AS实现了单片机在局域网内和通过局域网在因特网上的WEBSERVER。远端用户可以通过浏览器访问存储在单片机系统上的WEB页面．     

基于VxWorks的KAME协议栈Socket描述符的研究与扩展

通过对KAME协议栈的Socket机制进行研究,提出了一种扩展KAME协议栈的方法,修改了KAME协议栈中Socket描述符的实现机制。这种方法有效地按照要求扩充了IPv6 Socket的个数,在高性能的嵌入式系统上提高了IPv6的运行效率,在VxWorks操作系统上运行可靠,并可作为KAME协议栈的扩展应用于IPv6网络。