一种嵌入式系统UDPIP协议栈的优化设计

提出了一种简化高效的UDPIP协议栈的优化设计方法.从嵌入式系统所要求的高速传输效率出发,优化设计了协议栈的BUFFER管理系统、BSD接口、路由模块以及数据重组机制.从协议栈的可移植性出发,实现了UDPIP协议栈与标准ETH驱动的挂接,以及同基于其他物理介质的虚拟ETH驱动的挂接.与VXWORKS协议栈的性能对比结果...     

Formal Memory Models for the Verification of Low-Level Operating-System Code

This article contributes to the field of operating-systems verification. It presents a formalization of virtual memory that extends to memory-mapped devices. Our formalization consists of a stack of three detailed formal memory models: physical memory (i.e., RAM), physically-addressable memory-mapped devices (including their respective side effects, access and alignment requirements), and page-table based virtual memory. Each model is formally shown to satisfy the plain-memory specification, a memory abstraction that enables efficient reasoning for type-correct programs. This stack of memory models was developed in an attempt to verify Nova, the Robin micro-hypervisor. It is a key component of our verification environment for operating-system kernels based on the interactive theorem prover PVS.     

Java虚拟机中Java栈以及相关指令的实现

Java栈是Java虚拟机中运行时数据区的主要组成部分。大部分虚拟机指令的操作都与Java栈中的框架相关联。该文描述了Java栈在Java虚拟机运行中所起的作用,自行设计了一种Java栈的数据结构,提出了一些具有代表性的字节码指令的实现方法。同时总结了Java栈对虚拟机运行效率的影响。     

XML流上的关键字查询算法

针对当前XML流过滤研究中存在的问题,使用关键字查询方法作为解决方案。提出最右包含边界的概念,结合一个虚拟栈实现用于在XML数据流上进行关键字查询的XVirtual Stack算法。理论分析和实验结果证明,该算法具有高效性。     

一种虚拟路由器的体系结构及实现

提出了一种虚拟路由器体系结构，并对其中的关键组成部件如虚拟协议栈模块、虚拟路由协议模块以及虚拟管理模块等功能和实现进行了描述，为了实现单一代码能够运行多个实例，使用封装技术修改了协议栈代码、路由协议代码和路由器中其它的功能模块代码，并以BSD4.3为基础实现了虚拟路由器原型。通过对原型的测试，表明提出的体系结构和实现方法能够达到预期效果，具有实际应用价值。     

嵌入式Forth虚拟机架构的多任务调度算法设计与实现

针对嵌入式应用领域对操作系统在重构、扩展、移植、交互、安全、高效等方面日趋苛刻的现实需求及Forth系统所固有的特性,采用Forth虚拟机技术,对基于Forth虚拟机架构的嵌入式操作系统关键技术进行探索,提出一种具有良好扩展和移植特性、高效精简的基于Forth虚拟机架构的嵌入式多任务操作系统调度算法。该算法采用了以Forth虚拟机指令同步的协同式多任务调度机制,缩短了任务切换时间,将上下文切换操作简化为只需保存数据堆栈指针。实验结果表明,基于Forth虚拟机架构的多任务调度算法发挥了Forth系统所固有的特性,针对特定应用,提高了效率,适合资源有限的嵌入式环境。     

申威架构下的虚拟机访存特征提取方法

虚拟化技术是云服务的重要支柱之一,虚拟化充分扩展了物理资源的灵活性,提升了物理资源的利用率。随着国家信息化水平的发展,云服务器核心技术自主可控、安全高效的要求不断提高。近年来,作为国产服务器的典型代表,申威架构服务器的功能不断完善。提出了申威架构上的虚拟机访存特征提取方法,充分利用了申威架构独特优势,实时测算虚拟机的内存缺失率曲线,并最终计算工作集大小,同时利用热页集机制大幅度减少页面追踪的性能开销。实验结果表明,该方法可以准确计算虚拟机工作集大小,平均误差低于3%,平均性能开销不高于8.3%。本工作为申威虚拟机内存动态分配提供条件,最终目标是提高申威云服务器整体性能和内存利用率。     

Dalvik虚拟机在龙芯平台上的移植与实现

在分析Dalvik虚拟机的结构和运行机制的基础上,针对龙芯处理器平台,研究移植Dalvik虚拟机的关键技术,描述Dalvik解释器的执行流程与方法调用过程中解释器栈帧的作用,实现可以完整运行Android系统的龙芯Dalvik虚拟机。对移植后的Dalvik虚拟机进行性能分析,并给出后续优化方案。     

虚拟存储技术在容灾系统中的应用

基于对虚拟存储技术及其在容灾系统中应用现状的分析,设计一个适用于容灾系统的虚拟文件系统。该系统基于Windows平台,通过在Windows存储栈的层次式结构中添加过滤驱动层来实现上层文件系统与下层卷管理器的隔离。在过滤驱动层中,结合虚拟内存的映射原理和容灾系统的应用需求,实现适用于容灾系统的虚拟存储映射机制。     

Design and verification of a stack processor virtual component

Hardware and software codesign and flexibility requirements often necessitate embedded application-specific instruction-set processors in system-on-chip designs. Spaceman, a reusable stack-processor virtual component, offers a customer-configurable instruction set; parameterizable bus widths, stack depths, and stack access ranges; and selectable bus interfaces     

基于以太网交换机的Linux协议栈虚拟化技术

网络协议栈虚拟化的目标是在一台网络设备上虚拟出多个协议栈以实现网络设备的一虚多功能。由于 Linux操作系统的网络协议栈本身是不支持这种网络协议栈虚拟化技术的,因此本文通过对Linux操作系统3.11.10版本 IPV4网络协议栈进行改造以实现 Linux网络协议栈的虚拟化,并在设备平台上验证了经过网络协议栈虚拟化改造后的以太网交换机对业务流的隔离功能。     

Efficient exception handling in Java bytecode-to-C ahead-of-time compiler for embedded systems

One of the most promising approaches to Java acceleration in embedded systems is a bytecode-to-C ahead-of-time compiler (AOTC). It improves the performance of a Java virtual machine (JVM) by translating bytecode into C code, which is then compiled into machine code via an existing C compiler. One important design issue in AOTC is efficient exception handling. Since the excepting point and the exception handler may locate in different methods on a call stack, control transfer between them should be streamlined, while an exception would be an “exceptional” event, so it should not slow down normal execution paths. Previous AOTCs often employed a technique called stack cutting based on a setjmp()/longjmp() pair, which we found is involved with too much performance overheads. Also, when the AOTC and the interpreter are employed concurrently (e.g., some methods are AOTCed while other methods are interpreted), the performance of normal execution paths is affected more seriously. This paper proposes a simpler solution based on an exception check after each method call, merged with garbage collection check for reducing its overhead. Our evaluation results on SPECjvm98 on Sun's CVM indicate that our technique can improve the performance of stack cutting by more than 25%. A similar performance benefit can be noted on a hybrid execution environment of both the AOTC and the interpreter.     

基于堆栈式虚拟机的汇编器及连接器的设计与实现

以MULTOS虚拟机为例，论述了基于堆栈式虚拟机的汇编器及连接器的开发方法。首先介绍了MUEIDS虚拟机的体系结构，然后描述了如何综合运用词法分析器、语法分析器的自动构造工具Flex和Bison来开发虚拟机的汇编器，最后介绍了连接器的工作原理及实现。     

基于Windows NT核心态驱动实现虚拟存储管理若干问题研究

windows存储设备驱动程序是分层实现的 ,可以在多个驱动层次进行存储管理 .介绍了 windows NT存储设备驱动程序层次模型 ,对虚拟存储管理在中间驱动层次和适配器驱动层次的实现进行了阐述 ,并给出了在不同层次实现软阵列的实例 ,结合 I/ O测试结果对不同层次软阵列性能特点进行了分析评价     

Stack virtualization for source level debugging

The compilation of high‐level languages to general‐purpose execution platforms poses some challenges when it comes to debugging. Typically, abstractions that are not natively supported by the execution platform must be emulated with intermediate data structures and function calls. Unfortunately, the details of the emulation are visible in the execution stack, and this unwanted information greatly reduces the effectiveness of debuggers. This paper presents a general method for constructing a virtual view of the stack, in order to mask intermediate function calls that were generated to emulate high‐level abstractions, or even to recover logical frame information that was lost during the compilation process. In particular, virtual views enable the visualization of two disjoint code representations (e.g. native code and interpreted code) as a single unified stack. We illustrate this method by showing how to handle the compilation of Bigloo, a dialect of the Scheme programming language. Copyright © 2006 John Wiley & Sons, Ltd.     

On virtual private networks security design issues

The concept of virtual private networks (VPNs) provides an economical and efficient solution on communicating private information securely over public network infrastructure.In this paper, we discuss two issues on the design of VPN. We first propose the VPN services, the mandatory VPN operations for each VPN service and the design on VPN protocol stack.Afterwards, we propose a list of protocol modules to be used to support the VPN operations and co-relate the mandatory VPN operations to the appropriate VPN protocols. We then propose the design of VPN software that provides guarantees on security, connectivity and quality of service. We also discuss the message processing sequence by the VPN software.     

面向虚拟企业的VAN技术研究

虚拟企业信息系统中的安全问题目前缺乏一个整体的解决方案，文中提出了虚拟应用网络(VAN)的概念，描述了VAN在客户端的网络堆栈结构及实现，以及服务器上实现基于用户、基于应用的应用层路由控制模型。通过对VAN的研究和实施，可以为虚拟企业信息系统提供基于用户、基于应用的访问控制，为虚拟企业提供一个安全的、统一的、透明的网络平台。     

一种基于P2P机制的虚拟以太网改进设计与实现

传统基于C/S模式的虚拟以太网的数据在处理过程中需要两次经过协议栈,这在一定程度上影响了远程安全组网的传输效率.提出了一种改进的基于P2P机制的虚拟以太网设计,实现虚拟网络中节点之间的对等连接,能有效克服传统虚拟以太网的不足.测试表明,该设计提高了系统的通信效率,明显改善了虚拟以太网的传输性能.     

Elastos内存管理对软件调试的支持

软件调试支持是操作系统的重要组成部分,而由于内存管理不善造成的软件BUG占软件故障的很大比例。从内存管理的角度,讨论了Elastos操作系统对软件调试的支持。介绍了Elastos的内存布局和堆管理器算法,然后论述了堆、栈的内存管理,以及针对软件调试所提供的栈保护页设置、堆块前／后内存越界检查等。最后简要地介绍了构件Domain技术和基于伪驱动的内核窥探调试。通过Elastos内存管理的调试支持,可以提高修复和内存管理相关的BUG,增强软件的可靠性,减小软件的开发成本。