Linux互斥锁机制的研究及改进

Applications with real-time constraints are not only growing in the field of embedded system, but gaining popularity in the desktop environment as well. At the same time, using an opened source system ,Linux, as the sup-ported OS is more and more appealing to many developers. So it is regarded as a potential aspect by many users to im-prove Linux performance to satisfy the real-time requirements. The article discusses the mutex implementation of Linux in depth and on the basis of that, gives rise to methods to improve the deficiency. An implementation underversion of 2.2 series is brought forward.     

Hibernate Combined TableViewer in the Application of Medicines Inventory Management System

To solve the data persistence problem in the management system, this paper used the popular object-relational mapping framework Hibernate to achieve the persistence layer which in a medicines inventory management system. This paper described the advantages and principles of the Hibernate, and then showed the written work of the configuration files, mapping files, persistent classes, etc. Finally, the paper showed how to display the specific data information in the TableViewer based on the Eclipse RCP framework. It is observed that, operating the objects in the Hibernate framework is more flexible and efficient than using JDBC directly. Ad in addition, the application based on Eclipse RCP framework can take over many excellent features of Eclipse, and the developers can improve their efficiency by these features.     

Characterizing and Detecting Gas-Inefficient Patterns in Smart Contracts

Ethereum blockchain is a new internetware with tens of millions of smart contracts running on it.Different from general programs,smart contracts are decentralized,tamper-resistant and permanently running.Moreover,to avoid resource abuse,Ethereum charges users for deploying and invoking smart contracts according to the size of contract and the operations executed by contracts.It is necessary to optimize smart contracts to save money.However,since developers are not familiar with the operating environment of smart contracts(i.e.,Ethereum virtual machine)or do not pay attention to resource consumption during development,there are many optimization opportunities for smart contracts.To fill this gap,this paper defines six gas-inefficient patterns from more than 25,000 posts and proposes an optimization approach at the source code level to let users know clearly where the contract is optimized.To evaluate the prevalence and economic benefits of gas-inefficient patterns,this paper conducts an empirical study on more than 160,000 real smart contracts.The promising experimental results demonstrate that 52.75%of contracts contain at least one gas-inefficient pattern proposed in this paper.If these patterns are removed from the contract,at least 0.30 can be saved per contract.     

Improving Application Launch Performance on Solid State Drives

Application launch performance is of great importance to system platform developers and vendors as it greatly affects the degree of users’ satisfaction.The single most effective way to improve application launch performance is to replace a hard disk drive (HDD) with a solid state drive (SSD),which has recently become affordable and popular.A natural question is then whether or not to replace the traditional HDD-aware application launchers with a new SSD-aware optimizer.We address this question by analyzing the inefficiency of the HDD-aware application launchers on SSDs and then proposing a new SSD-aware application prefetching scheme,called the Fast Application STarter (FAST).The key idea of FAST is to overlap the computation (CPU) time with the SSD access (I/O) time during an application launch.FAST is composed of a set of user-level components and system debugging tools provided by Linux OS (operating system).Hence,FAST can be easily deployed in any recent Linux versions without kernel recompilation.We implement FAST on a desktop PC with an SSD running Linux 2.6.32 OS and evaluate it by launching a set of widely-used applications,demonstrating an average of 28% reduction of application launch time as compared to PC without a prefetcher.     

Developer social networks in software engineering:construction,analysis,and applications

With the increasing popularity of Internet, more and more developers are collaborating together for software development. During the collaboration, a lot of information related to software development, including communication and coordination information of developers, can be recorded in software repositories. The information can be employed to construct Developer Social Networks （DSNs） for facilitating tasks in software engineering. In this paper, we survey recent advances of DSNs and examine three fundamental steps of DSNs, namely construction, analysis, and applications. We summarize the state-of-the-art methods in the three steps and investigate the relationships among them. Furthermore, we discuss the main issues and point out the future opportunities in the study of DSNs.     

分布式协作模型及应用研究

With the development of the Web technology,the application environment has acquired many new characters such as dynamic, openness,distribution and information uncertainty.The processing mode of application systems is more complicated than ever.For example,it requires application systems to have more community processing ability,interactive ability,distributed processing ability and collaborative ability.Accordingly the research and development of the computer application system transited from client/server information processing system into distributed collaborative processing system based on Web.Especially in the environment where the information and resources are highly distributed,the accomplishment of complicated tasks is dependent more on the resources coordination,information sharing and coordinator collaboration.The collaboration is one aspect of the group behavior and its goal is to provide a optimal method to utilize the resource through the information interaction and to solve the task which couldn't be accomplished by each coordinator alone and get the more total benefits than the sum of each benefit.The collaboration problem is the important one for distributed tasks processing.This paper surveys,the research and application status of distributed collaborative models and several representative architectures of distributed collaborative processing are proposed.However,the existing problems and the future researching direction are presented.     

Towards a uniform cooperative platform: Cova approach and experience

A cooperative platform called Cova is presented, which aims to uniformly model a wide range of cooperation scenarios and to reduce the groupware design and development work. To achieve these goals, Cova provides two facilities, namely a specification language for developers to describe various cooperation modes uniformly and a run-time system that provides some general-purposed services guaranteeing the semantics specified. With these facilities, the developers can then concentrate on the application specific functions rather than the control mechanisms. There-fore, the development efficiency is promoted. This paper details the design and implementation issues of the platform including the model and the specification language, platform architecture,transaction management, service integration and so on. Application development with Cova plat-form is also covered.     

Bigflow: A General Optimization Layer for Distributed Computing Frameworks

As data volumes grow rapidly, distributed computations are widely employed in data-centers to provide cheap and efficient methods to process large-scale parallel datasets. Various computation models have been proposed to improve the abstraction of distributed datasets and hide the details of parallelism. However, most of them follow the single-layer partitioning method, which limits developers to express a multi-level partitioning operation succinctly. To overcome the problem, we present the NDD (Nested Distributed Dataset) data model. It is a more compact and expressive extension of Spark RDD (Resilient Distributed Dataset), in order to remove the burden on developers to manually write the logic for multi-level partitioning cases. Base on the NDD model, we develop an open-source framework called Bigflow, which serves as an optimization layer over computation engines from most widely used processing frameworks. With the help of Bigflow, some advanced optimization techniques, which may only be applied by experienced programmers manually, are enabled automatically in a distributed data processing job. Currently, Bigflow is processing about 3 PB data volumes daily in the data-centers of Baidu. According to customer experience, it can significantly save code length and improve performance over the intuitive programming style.     

Organizing Projects Around the Mitigation of Risks Arising from System Dynamic Behavior

Many of the key products and services used by modern societies are the result of large-scale engineering projects. Despite decades of theoretical and practical work in the art of systems engineering and project management, project execution results remain somewhat inconsistent, in the sense that many projects fail to produce a product that meets the original specifications, and many more projects achieve some measure of technical success only after taking significantly more time and/or money than originally expected. One source of such failures is the occurrence of unplanned and adverse dynamic behavior in the resulting system. This paper summarizes research being conducted to look at the potential of design-phase actions that centralize control of the eventual system''s dynamic behavior as a potential solution to some instances of this problem. This approach could lead to increased chances of success on future major system development projects, through a new method for instituting better control of the dynamic behavior of such a system.     

Energy Theft Detection in Smart Grids: Taxonomy,Comparative Analysis,Challenges, and Future Research Directions

Electricity theft is one of the major issues in developing countries which is affecting their economy badly.Especially with the introduction of emerging technologies,this issue became more complicated.Though many new energy theft detection(ETD)techniques have been proposed by utilising different data mining(DM)techniques,state&network(S&N)based techniques,and game theory(GT)techniques.Here,a detailed survey is presented where many state-of-the-art ETD techniques are studied and analysed for their strengths and limitations.Three levels of taxonomy are presented to classify state-of-the-art ETD techniques.Different types and ways of energy theft and their consequences are studied and summarised and different parameters to benchmark the performance of proposed techniques are extracted from literature.The challenges of different ETD techniques and their mitigation are suggested for future work.It is observed that the literature on ETD lacks knowledge management techniques that can be more effective,not only for ETD but also for theft tracking.This can help in the prevention of energy theft,in the future,as well as for ETD.     

一种基于改进时钟系统的Linux实时化方案

目前,实时领域的应用逐渐扩大,不仅传统的嵌入式系统需求日益紧迫,而且也渗透到桌面环境。而随着Linux操作系统的成功,改进Linux的设计和性能,使其应用于实时领域吸引了许多研究人员和开发人员的注意力。论文针对Linux时钟系统管理方面的研究,提出了一种针对时钟的改进算法,以此为基础,根据实时应用的特点,进一步给出一种调度算法的改进措施。试验证明,所做的改进有效地提高了Linux的调度精度,满足了软实时方面的需求。     

一种基于Linux操作系统下时钟系统的改进机制

随着Linux操作系统的成功,改进Linux的设计和性能,使其应用于实时领域受到了越来越多人的关注。考虑到Linux目前的时钟粒度仍然粗糙,它将直接影响到整个内核的实时性能,文中提出了一种基于Linux操作系统下时钟系统的改进机制,找出修改时钟系统提高实时性的具体方法。实验结果显示,所作改进以不大的代价有效地提高了Linux的实时性能。     

Linux输入子系统的分析与应用

Linux内核具有很多优秀的机制,在驱动方面,输入子系统为驱动开发者提供了一个框架,只需向内核上报底层相关硬件事件,这使得底层硬件开发的周期大大缩短.主要分析Linux 2.6.22.6内核版本所提供的输入子系统框架,并在此框架下做按键应用.     

Linux2.6下Makefile文件的分析与研究

由于Linux操作系统具有源代码开放性和内核可裁减性,软件开发者越来越多地编写基于Linux的应用程序,而编译环境的搭建显得尤为重要。本文主要介绍了Makefile文件的作用原理、语法规则及书写Makefile的几点注意事项,并针对2.6内核的特点对Makefile文件进行了分析和研究。     

Assessing the health of open source communities

Before contributing to a free or open source software project, understand the developers, leaders, and active users behind it. The computing world lauds many Free/Libre and open source software offerings for both their reliability and features. Successful projects such as the Apache httpd Web server and Linux operating system kernel have made FLOSS a viable option for many commercial organizations. While FLOSS code is easy to access, understanding the communities that build and support the software can be difficult. Despite accusations from threatened proprietary vendors, few continue to believe that open source programmers are all amateur teenaged hackers working alone in their bedrooms. But neither are they all part of robust, well-known communities like those behind Apache and Linux.     

通过设计模式构造的通信应用服务框架

由于通信软件内在的复杂性，通信软件的开发者通常需要面对诸多挑战，而利用针对通信软件的设计模式可以帮助软件开发者克服困难，开发出高性能的通信软件。本篇论文将阐释我们是如何利用针对通信软件的设计模式来开发出一个基于Linux的通信应用服务器框架的。     

基于at91sam 9g 25的Linux下RTC设备驱动的设计与实现

I2C总线以其简单高效的方式被广泛的运用在嵌入式产品设计中,而实时时钟RTC则是其中应用的典型代表。在嵌入式Linux系统中,对其I2C驱动程序提供了较好的支持框架。但随着Linux内核版本的不断升级,对于I2C设备驱动的结构设计也趋于复杂,往往让开发者有些不知所措。本文以2.6.39版本Linux内核为背景,在分析该Linux版本I2C总线设备结构和RTC设备资源的基础上,结合RTC设备驱动模型和I2C/SMBus传输方式,对RTC设备在at91sam9g25上进行了具体的设备驱动设计实现,并通过在电力用户集中器设备中的应用,证明了驱动设计的可行性。     

开源软件开发者的演化研究

开源软件的开发主要依靠开发人员的自我管理和志愿贡献。在软件开发过程中,开发人员的组成、分工、能力等会发生经常性的改变,这些改变都会通过交互行为的变化反映出来。已有研究成果表明开源软件存在核心团队,他们主导项目的开发与实施,但对开发团队随时间而发生的结构变化的研究较少。通过观测软件项目生命周期中开发者总体的变化情况,研究了开发者网络与软件的协同演化机理,以GNU/Linux公共数据集为例,讨论了开源软件开发者数量、自愿度、开发者经验与项目的协同演化现象,并给出了演化的合理解释。     

基于SCTP的客户/服务器的设计与实现

随着IP网向多业务网的发展,新一代运输层协议SCTP会逐渐替代TCP在下一代网络中获得更加广泛的应用。分析了SCTP/IP协议栈中数据传输过程,介绍了SCTP协议所提供给开发人员的套接口编程模型,并给出一个在Uinx/Linux系统上利用一到多形式套接口模型开发客户/服务器应用的示例。