采用统一接口采集Linux内核信息的方法研究

Linux操作系统本身为用户程序提供了大量接口用于采集内核信息,每一种类型的内核信息都有一个相应的接口。一个对Linux内核进行全面监控的监控系统需要采集大量的内核信息,这就需要调用大量的接口,这给监控系统带来了很大的复杂性。文中提出了一种采用统一接口采集内核信息的方法,并对其进行了研究与实现,采用这种方法。用户程序从同一个接口可以采集到所有的内核信息,简化了用户程序对内核信息的访问。     

Linux新型内核防火墙及在校园网中的应用

介绍了防火墙的基本概念及其分类,阐述了Linux2．4版新型内核防火墙netfilter框架的工作机制及一个基于Netfilter框架的、称为iptables的数据报选择系统在Linux2．4内核中的实现方法,最后给出了netfilter实现校园网防火墙的一个应用实例。     

Linux动态内核补丁技术及其安全性分析

为了能在运行状态对Linux系统内核功能进行修改,介绍两种动态内核补丁技术：LKM和／dev／kinem,并且给出了简单的实现,同时对它们所带来的安全隐患进行了分析,给出了相应的解决方案。     

Common coupling and pointer variables,with application to a Linux case study

Both common coupling and pointer variables can exert a deleterious effect on the quality of software. The situation is exacerbated when global variables are assigned to pointer variables, that is, when an alias to a global variable is created. When this occurs, the number of global variables increases, and it becomes considerably harder to compute quality metrics correctly. However, unless aliasing is taken into account, variables may incorrectly appear to be unreferenced (neither defined nor used), or to be used without being defined. These ideas are illustrated by means of a case study of common coupling in the Linux kernel.

Deadline scheduling in the Linux kernel

During the last decade, there has been a considerable interest in using Linux in real‐time systems, especially for industrial control. The simple and elegant design of Linux guarantees reliability and very good performance, while its open‐source license allows to modify and change the source code according to the user needs. However, Linux has been designed to be a general‐purpose operating system. Therefore, it presents some issues like unpredictable latencies and limited support for real‐time scheduling. In this paper, we present our experience in the design and implementation of the real‐time scheduler that has been recently included in the Linux kernel. The scheduler is based on the Resource Reservation paradigm, which allows to enforce temporal isolation between the running tasks. We describe the genesis of the project, the challenges we have encountered, the implementation details and the API offered to the programmers. Then, we show the experimental results measured on a real hardware. Copyright © 2015 John Wiley & Sons, Ltd.     

模糊核覆盖分类器及其应用*

核覆盖算法是一种性能优秀的分类算法,但在拒识点处理方面存在不足。对核覆盖算法的构造过程进行了分析,修改了算法中覆盖半径的选取原则,对拒识样本引入隶属度函数,将算法推广为模糊核覆盖算法。讨论了孤立覆盖对分类器的影响,对覆盖数进行精简,降低计算量。通过实验验证改进算法的性能,并与其他模糊分类方法进行对比。将模糊核覆盖算法应用于垃圾邮件过滤,实验结果表明过滤器的性能得到了有效提高。     

Linux内核启动过程分析

结合Linux内核代码,分析了80x86平台上Linux操作系统内核的启动过程,特别对内核的动态加载、CPU工作模式的转换以及内存分页机制最终启动的全过程做了较为细致的阐述.该分析有助于更深入地了解Linux内核的工作原理和多任务操作系统的实现机理,是将Linux运用于嵌入式系统的前期工作.     

Sequential kernel density approximation and its application to real-time visual tracking

Visual features are commonly modeled with probability density functions in computer vision problems, but current methods such as a mixture of Gaussians and kernel density estimation suffer from either the lack of flexibility, by fixing or limiting the number of Gaussian components in the mixture, or large memory requirement, by maintaining a non-parametric representation of the density. These problems are aggravated in real-time computer vision applications since density functions are required to be updated as new data becomes available. We present a novel kernel density approximation technique based on the mean-shift mode finding algorithm, and describe an efficient method to sequentially propagate the density modes over time. While the proposed density representation is memory efficient, which is typical for mixture densities, it inherits the flexibility of non-parametric methods by allowing the number of components to be variable. The accuracy and compactness of the sequential kernel density approximation technique is illustrated by both simulations and experiments. Sequential kernel density approximation is applied to on-line target appearance modeling for visual tracking, and its performance is demonstrated on a variety of videos.     

Linux内核函数鲁棒性关联测试

在简要介绍软件鲁棒性基准程序测试方法的基础上,以Linux操作系统内核函数为例,通过对用于分析测试结果的维度模型进行分析,提出了软件鲁棒性的关联测试方法,并给出了相应的测试实例及测试结果,为Linux操作系统内核函数鲁棒性测试提供了更为直观、有效的方法.     

Linux内核内存管理机制和改进

理解和掌握Linux内核内存基本知识对学习Linux是至关重要的,Linux内核内存是学习Linux内核的基础,对于学习Linux其他方面的内容很有帮助,本文将主要介绍有关Linux内核内存两方面的内容,即内存管理机制及其改进。在内存管理机制中,主要介绍了分段机制和分页机制,它们是所有内存管理的基础,之后所有对内存管理的改进都是以分段机制和分页机制为基础的。在内存管理的改进中,介绍了三个主要的内容,即:反向映射,大内存页和在高端内存中存储页表条目。     

Timing analysis of the PREEMPT RT Linux kernel

In the theory of real‐time scheduling, tasks are described by mathematical variables, which are used in analytical models in order to prove schedulability of the system. On real‐time Linux, tasks are computer programs, and Linux developers try to lower the latencies caused by the Linux kernel, trying to achieve faster response for the highest‐priority task. Although both seek temporal correctness, they use different abstractions, which end up separating these efforts in two different worlds, making it hard for the Linux practitioners to understand and apply the formally proved models to the Linux kernel and for theoretical researchers to apply the restrictions imposed by Linux for the theoretical models. This paper traces a parallel between the theory of response‐time analysis and the abstractions used in the Linux kernel. The contribution of this paper is threefold. We first identify the PREEMPT RT Linux kernel mechanisms that impact the timing of real‐time tasks and map these impacts to the main abstractions used by the real‐time scheduling theory. Then, we describe a customized trace tool, based on the existing trace infrastructure of the Linux kernel, that allows the measurement of the delays associated with the main abstractions of the real‐time scheduling theory. Finally, we use this customized trace tool to characterize the timing lines resulting from the behavior of the PREEMPT RT Linux kernel. Copyright © 2015 John Wiley & Sons, Ltd.     

Linux内核防火墙研究与实现

Linux提供的基于内核的netfilter框架,具有通用性和可扩展性的特点,使得开发人员可结合自己的网络安全要求,在适当的位置上登记一些需要的处理函数,实现用户自己开发防火墙。本文主要分析Linux2.4netfilter的实现机制,并结合实例说明如何编写自己的内核并将其应用到netfilter的架构中,以实现自己的定制防火墙功能。对于大多数缺乏资金预算的企事业单位,结合单位实际自主开发防火墙,保护内网安全确实是一个性价比较高的选择。     

Linux抢占式内核的研究与实现

随着Linux操作系统的成功应用,尤其是在嵌入式实时应用领域,Linux实时性能的提高成为一个很重要的因素.系统核心的可抢占性是决定系统实时性能的一个重要条件,而Linux的核心是不可抢占的,通过将Linux的内核改造为可抢占式内核,可缩短系统的响应延时,提高Linux的实时性.分析了几种实现抢占式内核的方法,介绍了一种实现Linux可抢占式内核的方法,并对其实现细节进行了详细的说明.     

RBF核SVM及其应用研究

因其核函数的良好性态,RBF核SVM（RBF-SVM）在实际应用中表现出良好的学习性能,但是RBF核函数中的参数对SVM的性能起决定性作用.阐述了RBF-SVM的性能随着变化而变化的规律,并将RBF-SVM引入自动羽绒识别系统中.根据自动羽绒识别系统的实际需求和RBF-SVM的性能变化规律,论述了本系统中参数的选取依据和选取过程,并且给出了的相关曲线变化图.通过研究,最后得到适合本系统的识别模型,从而提高了系统的总体识别率.同时,也验证了RBF-SVM的良好特性和其受参数的约束规律.     

Linux 2.6内核的内核对象机制分析

文中介绍了Linux2.6内核中管理设备及其驱动程序的内核对象机制,重点分析了该机制的主要数据结构、工作原理和操作函数。提出了基于嵌入应用时简化目录结构的方法。     

Object‐oriented wrappers for the Linux kernel

Linux is an open‐source operating system, which has increased in its popularity and size since its birth. Various studies have been conducted in literature on the evolution of the Linux kernel, which have shown that there are considerable maintenance problems arising out of the coupling issues in the Linux kernel and this may hamper the evolution of the kernel in future. We propose an object‐oriented (OO) wrapper‐based approach to Linux kernel to provide OO abstractions to external modules. As the major growth of the size of the Linux kernel is in device drivers, our approach provides substantial benefits in terms of developing the device drivers in C++, although the kernel is in C. Providing reusability and extensibility features to device drivers improves the maintainability of the kernel. The OO wrappers provide several benefits to module developers in terms of understandability, development ease, support for OO modules, etc. The design and implementation of C++ wrappers for Linux kernel and the performance of a device driver re‐engineered in C++ are presented in this paper. Copyright © 2008 John Wiley & Sons, Ltd.     

Analysing the Linux kernel feature model changes using FMDiff

Evolving a large scale, highly variable system is a challenging task. For such a system, evolution operations often require to update consistently both their implementation and its feature model. In this context, the evolution of the feature model closely follows the evolution of the system. The purpose of this work is to show that fine-grained feature changes can be used to guide the evolution of the highly variable system. In this paper, we present an approach to obtain fine-grained feature model changes with its supporting tool “FMDiff”. Our approach is tailored for Kconfig-based variability models and proposes a feature change classification detailing changes in features, their attributes and attribute values. We apply our approach to the Linux kernel feature model, extracting feature changes occurring in sixteen official releases. In contrast to previous studies, we found that feature modifications are responsible for most of the changes. Then, by taking advantage of the multi-platform aspect of the Linux kernel, we observe the effects of a feature change across the different architecture-specific feature models of the kernel. We found that between 10 and 50 % of feature changes impact all the architecture-specific feature models, offering a new perspective on studies of the evolution of the Linux feature model and development practices of its developers.     

Linux核心动态模块技术的分析

核心动态模块技术是Linux操作系统设计上的一个重要特色,它允许一些模块动态地加载和卸载,核心不需要重新编译和启动。为支持动态可加载模块,Linux在核心提供了相应的数据结构和系统调用,以及对目标模块中的符号进行处理和对模块相关性进行处理。本文分析了动态模块的主要实现技术,对现代操作系统的研究和设计有一定的指导意义。     

Linux内核参数对Spark负载性能影响的研究

关于Spark性能的研究目前正在成为热点,但调优策略多位于应用层,而不是系统层。操作系统作为硬件之上的第一层软件,对硬件性能发挥起着根本作用。Linux内核提供了丰富的参数作为优化性能的接口,但实际中,这些参数的作用并没有得到充分发挥。人们更多是采用系统默认值,而不是根据具体环境进行调整。然而本文实验发现,系统默认值并不一定是最好的选择,有时甚至是最坏的。定义了"影响比"这一概念,并基于此概念提出了一种通过分析内核函数的执行情况来认识参数对Spark应用影响的方法。针对Spark内存计算的特点,从大页、NUMA这两个与使用内存紧密相关的方面分析了相关内核参数对几种典型Spark负载的性能影响,并由此得出一些结论。希望本文的分析和结论可以为Spark平台合理设置内核参数提供一些参考。