TreadMarks is a distributed shared memory (DSM) system for standard Unix systems such as SunOS and Ultrix. This paper presents a performance evaluation of TreadMarks running on Ultrix using DECstation-5000/240's that are connected by a 100-Mbps switch-based ATM LAN and a 10-Mbps Ethernet. Our objective is to determine the efficiency of a user-level DSM implementation on commercially available workstations and operating systems. We achieved good speedups on the 8-processor ATM network for Jacobi (7.4), TSP (7.2), Quicksort (6.3), and ILINK (5.7). For a slightly modified version of Water from the SPLASH benchmark suite, we achieved only moderate speedups (4.0) due to the high communication and synchronization rate. Speedups decline on the 10-Mbps Ethernet (5.5 for Jacobi, 6.5 for TSP, 4.2 for Quicksort, 5.1 for ILINK, and 2.1 for Water), reflecting the bandwidth limitations of the Ethernet. These results support the contention that, with suitable networking technology, DSM is a...

1. Introduction ...SVM is an alias of softDSM. In the rest of this technical report, we will use them interchangely. Although the hardware approach to implement DSM has been shown to perform quite well, it requires a high engineering cost. SVM, on the other hand, is a cost-effective method to provide the shared memory abstraction on networks of workstations since it requires no special hardware support and is easy to implement. In this chapter, A survey of SVM system is presented. General concept of SVM is described in the following section. Some important issues in SVM are listed in section 3. From the six different facets, we compare 20 representative software DSM systems in section 4. Recent progress and future directions are listed in section 5. 2 Basic Idea of Shared Virtual Memory

In order to exploit the latest advances in hardware technology, application developers need high-performance, easy-to-use cooperation tools that span interconnections of standard hardware. Distributed shared memory has been proposed as such a cooperation tool, but performance problems have limited its usefulness. This paper argues that a new approach to distributed shared memory implementation can make it a effective tool in its own right and a foundation for other tools. It describes a prototype implementation that allows sharing of memory resources in a workstation cluster. The prototype is based on an innovative, low-overhead messaging protocol which utilizes the high bandwidth of the underlying hardware, while adding very little latency overhead. Finally, the interface exported by this software is designed to function effectively as a substrate for a variety of cooperation tools. 1: Introduction Clustered workstations offer the same potential peak processing power as a modern mult...

Simple COMA is a method for sharing address spaces among different nodes of a distributed memory computer. This method provides high performance without the complex and costly changes required by other shared memory organizations. It also retains the positive attributes of a distributed memory multicomputer, such as scalability and high availability. This paper explains the Simple COMA shared memory architecture and the potential implementation of this architecture on the IBM RS/6000 SP parallel computer. Background v1.2.8 scoma.doc 1 1 Background The IBM RS/6000 Scalable POWERparallel Systems (SP) is a distributed memory system comprised of separate, full function nodes. Each node's memory is addressable only from the processor(s) in that node. Each node is controlled by a separate kernel, and message passing is used for communication between nodes. On current SP systems, parallel programs which share data between multiple nodes do so explicitly via one of the various message pa...

Simple COMA is a method for sharing address spaces among different nodes of a distributed memory computer. This method provides high performance without the complex and costly changes required by other shared memory organizations. It also retains the positive attributes of a distributed memory multicomputer, such as scalability and high availability. This paper explains the Simple COMA shared memory architecture and the potential implementation of this architecture on the IBM RS/6000 SP parallel computer. Table of Contents 1 Background 1.1 Shared Memory Programming 1.2 The Simple COMA Architecture 2 S-COMA Details 2.1 Specifying Global Memory 2.2 Extending the Memory Hierarchy 2.3 Recognizing References to Global Memory 2.4 Maintaining Coherence 2.5 Homes for Global Data 3 Shared Memory Architectures 3.1 CC-UMA 3.2 CC-NUMA 3.3 NCC-NUMA 3.4 COMA 3.5 DVSM 4 References ...