DSM系统中内存一致性模型的研究

文章首先回顾了分布式共享存储器（ＤＳＭ）系统中主要的内存一致性协议,重点分析了释放一致性（ＲＣ）模型。在此模型的基础上对其进行了改进,提出了基于动态减少无效副本集的ＲＣ模型。     

A Low Overhead Logging Scheme for Fast Recovery in Distributed Shared Memory Systems

This paper presents an efficient, writer-based logging scheme for recoverable distributed shared memory systems, in which logging of a data item is performed by its writer process, instead of every process that accesses the item logging it. Since the writer process maintains the log of data items, volatile storage can be used for logging. Only the readers' access information needs to be logged into the stable storage of the writer process to tolerate multiple failures. Moreover, to reduce the frequency of stable logging, only the data items accessed by multiple processes are logged with their access information when the items are invalidated, and also semantic-based optimization in logging is considered. Compared with the earlier schemes in which stable logging was performed whenever a new data item was accessed or written by a process, the size of the log and the logging frequency can be significantly reduced in the proposed scheme.     

基于分布式共享存储器的并行程序设计

本文概述了分布式并行系统和分布式共享存储器的一般概念，讨论了使用共享对象和可靠广播的并行程序设计模型，最后给出了我们的改进模型。     

Optimizing OpenMP Programs on Software Distributed Shared Memory Systems

This paper describes compiler techniques that can translate standard OpenMP applications into code for distributed computer systems. OpenMP has emerged as an important model and language extension for shared-memory parallel programming. However, despite OpenMP's success on these platforms, it is not currently being used on distributed system. The long-term goal of our project is to quantify the degree to which such a use is possible and develop supporting compiler techniques. Our present compiler techniques translate OpenMP programs into a form suitable for execution on a Software DSM system. We have implemented a compiler that performs this basic translation, and we have studied a number of hand optimizations that improve the baseline performance. Our approach complements related efforts that have proposed language extensions for efficient execution of OpenMP programs on distributed systems. Our results show that, while kernel benchmarks can show high efficiency of OpenMP programs on distributed systems, full applications need careful consideration of shared data access patterns. A naive translation (similar to OpenMP compilers for SMPs) leads to acceptable performance in very few applications only. However, additional optimizations, including access privatization, selective touch, and dynamic scheduling, resulting in 31% average improvement on our benchmarks.     

基于分布/共享内存层次结构的并行程序设计

分布内存结构和共享内存结构各具特点,又有很强的互补性,分布／共享内存层次结构将两种结构相结合,以充分发挥其优势。文中主要讨论基于分布／共享内存层次结构的并行程序设计问题,介绍了MPI和OpenMP混合并行程序设计模式。     

软件DSM系统的重放

软件DSM系统的并行调试环境已经成为制约其广泛应用的一个重要因素，重放方法使得用户能用循环调试技术来调试具有执行不确定性的软件DSM程序，本文定义了软件DSM程序执行的happen-before-1关系，并依据其提出一种在软件DMS系统JIAJIA上实现重放的方法，实际应用测试表明，该方法产生很小的空间和时间开销。     

A Transparent Distributed Shared Memory for Clustered Symmetric Multiprocessors

A transparent distributed shared memory (DSM) system must achieve complete transparency in data distribution, workload distribution, and reconfiguration respectively. The transparency of data distribution allows programmers to be able to access and allocate shared data using the same user interface as is used in shared-memory systems. The transparency of workload distribution and reconfiguration can optimize the parallelism at both the user-level and the kernel-level, and also improve the efficiency of run-time reconfiguration. In this paper, a transparent DSM system referred to as Teamster is proposed and is implemented for clustered symmetric multiprocessors. With the transparency provided by Teamster, programmers can exploit all the computing power of the clustered SMP nodes in a transparent way as they do in single SMP computer. Compared with the results of previous researches, Teamster can realize the transparency of cluster computing and obtain satisfactory system performance.     

软件DSM系统中的动态数据竞争检测

数据竞争是共享存储程序中的一类难于调试的错误 .在支持域存储一致性模型的软件 DSM系统 JIAJIA上 ,通过采用汇编代码装配技术来获得程序所读写的共享变量集合的方法 ,实现了基于锁集合的动态数据竞争检测算法 .利用本文方法 ,在 TSP和 Barnes程序中找到了数据竞争情况 ,并根据找到的数据竞争 ,修正了 Barnes中的错误 .实际使用经验表明 ,本文方法易于用户使用 ,达到了实用水平     

可恢复的软件DSM系统JIACKPT

软件DSM(distributed shared memory)系统在机群上构造了共享存储编程环境,结合了共享存储的易编程性和机群的可扩展性,引起了广泛的研究.由于软件DSM系统是一个分布式系统,系统失败风险大,需要实现容错技术以促进其实用化.利用用户级检查点技术,在支持域存储一致模型的软件DSM系统JIAJIA的基础上,设计并实现了一个可恢复的高可移植的软件DSM系统JIACKPT(JIAjia with ChecKPoinTing).由于采用适合软件DSM系统的强全局一致状态以及多种优化措施,JIACKPT易于实现且获得很好的性能.在一个8节点的PC机群上的应用测试表明,即使每分钟做一次检查点,大部分应用的检查点开销也小于10%.此外,JIACKPT还具有高可移植性.这些都表明JIACKPT已经成为一个比较实用的系统.     

虚拟共享存贮器的一种实现策略

本文介绍了虚拟共享存贮器的概念及构成，提出了用动态分布管理者算法构造虚拟共享存贮器的实现策略。     

Distributed Monitoring of Concurrent and Asynchronous Systems*

In this paper we study the diagnosis of distributed asynchronous systems with concurrency. Diagnosis is performed by a peer-to-peer distributed architecture of supervisors. Our approach relies on Petri net unfoldings and event structures, as means to manipulate trajectories of systems with concurrency. This article is an extended version of the paper with same title, which appeared as a plenary address in the Proceedings of CONCUR2003.*This work was supported by the RNRT project MAGDA2, funded by the Ministère de la Recherche; other partners of the project are France Telecom R&D, Alcatel, Ilog, and Paris- Nord University.     

Scaling out NUMA-Aware Applications with RDMA-Based Distributed Shared Memory

Journal of Computer Science and Technology - The multicore evolution has stimulated renewed interests in scaling up applications on shared-memory multiprocessors, significantly improving the...     

基于共享内存的PowerPC系统BSP设计

板级支持包(BSP)介于主板硬件和操作系统之间,其功能与PC机上的BIOS相类似,主要完成硬件初始化并切换到相应的操作系统.因此它要求程序员不仅对软件而且对硬件和操作系统都要有一定的了解.该文介绍了基于共享内存的PowerPC系统BSP的程序设计,并已成功运行在PowerPC7447A处理器平台上.     

以操作系统为中心的存储一致性模型--线程一致性模型

分布共享存储系统为保证程序的正确执行，必须通过存储一致性模型对共享存储访问顺序加以限制，而现有模型在可扩展性和操作系统级实现方面存在不足。结合多线程的特点，提出了一种以操作系统为中心的线程一致性模型，通过并行程序执行过程中线程状态的变化来观察和限制存储访问事件的正确顺序，有利于系统的可扩展性、一致性维护信息获取的方便性和完备性以及操作系统本身的设计和实现。分别从模型的定义、正确性证明、实现方案和性能分析等几个方面展开了论述。     

分布共享存储的遥感图像并行预处理系统结构研究

随着遥感技术的发展,遥感图像的分辨率和采样率越来越高,对遥感图像预处理系统性能的要求也日益提高。本文介绍一种能高效实现遥感图像预处理的分布共享存储并行处理系统结构。     

一种面向多核DSP的小容量紧耦合快速共享数据池

该文结合片上便笺式存储器(SPM)的结构特点,提出了一种面向异构多核DSP的新型小容量紧耦合共享存储结构——快速共享数据池(FSDP).FSDP在存储层次上与一级Cache平行,可以被访存指令直接访问,采用多体并行的结构、交叉访问模式和基于硬件信号灯的自动同步机制,支持多个DSP核的并行访问与快速的核间数据交换,两核之间交换单个数据只需4拍.该文构建了FSDP的模拟模型,并进行了RTL级设计实现和分析.多种典型测试程序的验证表明,FSDP对于DSP核间细粒度共享数据的传输具有很高的效率,相比同类的VS-SPM结构能够将程序性能提高37%,与传统的共享数据Cache结合使用能够将异构多核DSP的性能提高13%.     

CAS-DSM: A Compiler Assisted Software Distributed Shared Memory

Traditional software Distributed Shared Memory (DSM) systems rely on the virtual memory management mechanisms to detect accesses to shared memory locations and maintain their consistency. The resulting involvement of the OS (kernel) and the associated overhead which is significant, can be avoided by careful compile time analysis and code instrumentation. In this paper, we propose such a Compiler Assisted Software support approach (CAS-DSM). In the CAS-DSM implementation, the involvement of the OS kernel is avoided by instrumenting the application code at the source level. The overhead caused by the execution of the instrumented code is reduced through several aggressive compile time optimizations. Finally, we also address the issue of reducing certain overheads in polling-based implementation of receiving asynchronous messages. We used SUIF, a public domain compiler tool, to implement compile time analysis, instrumentation and optimizations. We modified CVM, a publicly available software DSM to support the instrumentation inserted by the compiler. Detailed performance evaluation of CAS-DSM is reported using a set of Splash/Splash2 parallel application benchmarks on a distributed memory IBM SP-2 machine. CAS-DSM achieved moderate to good performance improvements for most of the applications compared to the original CVM implementation. Reducing the overheads in polling-based implementation improves the performance of CAS-DSM significantly resulting in an overall improvement of 12–52% over the original CVM implementation.     

多核处理器中混合分布式共享存储空间的实时划分技术

在多核处理器芯片中,分布式共享存储DSM虽然提供了统一的全局寻址的存储空间,但却引入了虚地址向实地址转换的开销,这对性能产生了负面的影响。我们注意到,在并行程序的执行过程中,被处理的数据属性(私有或共享)并不是一成不变的。并行程序中不同的数据具有不同的属性,即使同一数据在程序的不同执行阶段也可能具有不同的属性。本文首先详细地阐述了一种混合式的分布式共享存储空间,支持对共享数据采用全局寻址的虚地址访问而对私有数据采用快速寻址的实地址访问;进而提出了一种针对混合式的分布式共享存储空间的实时划分技术。该技术根据并行程序中数据的属性,在程序运行时,实时地调整和划分分布式共享存储空间。当数据为私有时,通过实地址访问加快数据的访问速度,当数据为共享时则维持虚地址访问,从而减少整个并行程序运行过程中的地址转换开销,提高系统的性能。实际应用程序的实验结果表明,与传统的分布式共享存储空间相比,实时划分的混合式的分布式共享存储空间具有性能优势,性能的提升比例与具体的网络规模、计算规模、并行程序映射方式等有关。在我们的实验中,性能的提升比例最高为13.14%,最低为6.98%。     

分布式数据库一致性维护算法

提出了一种维护分布式数据库的算法,克服了其他算法通信开销大、事务平均响应时间长、数据版本多等问题。该算法能保证原子数据的一致性,减少网络中的通信量,避免死锁的发生。