Many distributed systems for wide­area networks can be built conveniently, and operate efficiently and correctly, using a weak consistency group communication mechanism. This mechanism organizes a set of principals into a single logical entity, and provides methods to multicast messages to the members. A weak consistency distributed system allows the principals in the group to differ on the value of shared state at any given instant, as long as they will eventually converge to a single, consistent value. A group containing many principals and using weak consistency can provide the reliability, performance, and scalability necessary for wide­area systems. I have developed a framework for constructing group communication systems, for classifying existing distributed system tools, and for constructing and reasoning about a particular group communication model. It has four components: message delivery, message ordering, group membership, and the application. Each component may have a different implementation, so that the group mechanism can be tailored to application requirements. The framework supports a new message delivery protocol, called timestamped anti­entropy, which provides reliable, eventual message delivery; is efficient; and tolerates most transient processor and network failures. It can be combined with message ordering implementations that provide ordering guarantees ranging from unordered to total, causal delivery. A new group membership protocol completes the set, providing temporarily inconsistent membership views resilient to up to k simultaneous principal failures. The Refdbms distributed bibliographic database system, which has been constructed using this framework, is used as an example. Refdbms databases can be replicated on many different sites, using the group communication system described here.

Communication between processors has long been the bottleneck of distributed network computing. However, recent progress in switch-based high-speed Local Area Networks (LANs) may be changing this situation. Asynchronous Transfer Mode (ATM) is one of the most widely-accepted and emerging high-speed network standards which can potentially satisfy the communication needs of distributed network computing. In this paper, we investigate distributed network computing over local ATM networks. We first study the performance characteristics involving end-to-end communication in an environment that includes several types of workstations interconnected via a Fore Systems' ASX-100 ATM Switch. We then compare the communication performance of four different Application Programming Interfaces (APIs). The four APIs were Fore Systems ATM API, BSD socket programming interface, Sun's Remote Procedure Call (RPC), and the Parallel Virtual Machine (PVM) message passing library. Each API represents distribute...

Over the past few years, Transmission Control Protocol (TCP) has become the most widely used transport layer protocol on the Internet. TCP performs poorly however, if one of the communicating hosts is a mobile wireless computer [6]. One way to address this performance problem is to modify TCP to make it aware of host mobility. Such an approach

This paper presents a novel disk storage architecture called DCD, Disk Caching Disk, for the purpose of optimizing I/O performance. The main idea of the DCD is to use a small log disk, referred to as cache-disk, as a secondary disk cache to optimize write performance. While the cache-disk and the normal data disk have the same physical properties, the access speed of the former differs dramatically from the latter because of different data units and different ways in which data are accessed. Our objective is to exploit this speed difference by using the log disk as a cache to build a reliable and smooth disk hierarchy. A small RAM buffer is used to collect small write requests to form a log which is transferred onto the cache-disk whenever the cache-disk is idle. Because of the temporal locality that exists in office/engineering work-load environments, the DCD system shows write performance close to the same size RAM (i.e. solid-state disk) for the cost of a disk. Moreover, the cache...

Simultaneous Multithreading machines benefit from jobscheduling software that monitors how well coscheduled jobs share CPU resources, and coschedules jobs that interact well to make more efficient use of those resources. As a result, informed coscheduling can yield significant performance gains over naive schedulers. However, prior work on coscheduling focused on equal-priority job mixes, which is an unrealistic assumption for modern operating systems.

The basic virtual memory-mapped communication (VMMC) model provides protected, direct communication between the sender's and receiver's virtual address spaces, but it does not support high-level connection-oriented communication APIs well. This paper presents VMMC-2, an extension to the basic VMMC.We describe the design, implementation, and evaluate the performance of three mechanisms in VMMC-2: (1) a user-managed TLB mechanism for address translation which enables user libraries to dynamically manage the amount of pinned space and requires only driver support from many operating systems# (2) a transfer redirection mechanism whichavoids copying on the receiver 's side# (3) a reliable communication protocol at the data link layer whichavoids copying on the sender's side. Tovalidate our extensions we implemented stream sockets on top of the VMMC-2 running on a Myrinet network of Pentium PCs. This zero-copysockets implementation provides a maximum bandwidth of over 84 Mbytes/s and a one-way latency of 20 µs.

Despite the emergence of high speed LANs, the communication performance available to applications on workstation clusters still falls short of that available on MPPs. A new generation of efficient messaging layers is needed to take advantage of the hardware performance and to deliver it to the application level. Communication software is the key element in bridging the communication performance gap separating MPPs and workstation clusters. MPI-FM is a high performance implementation of MPI for networks of workstations connected with a Myrinet network, built on top of the Fast Messages (FM) library. Based on the FM version 1.1 released in Fall 1995, MPI-FM achieves a minimum oneway latency of 19 ¯s and a peak bandwidth of 17.3 MByte/s with common MPI send and receive function calls. A direct comparison using published performance figures shows that MPI-FM running on SPARCstation 20 workstations connected with a relatively inexpensive Myrinet network outperforms the MPI implementations a...

This thesis describes demand-based coscheduling, a new approach to scheduling parallel...

Data Type. A collection of operations, each with a name and a signature defining the number and types of its arguments. application domain A domain whose purpose is to execute an application program. binding An association of a name with some value; in IDC, the local data structures for invoking an operation on an interface. class A set of objects sharing the same implementation. An object is an instance of exactly one class. closure The concrete realisation of an interface. A record containing two pointers, one to an operation table and the other to a state record. concrete type A data type whose structure is explicit. constructor An operation on an interface which causes the creation of an object, and returns the interfaces exported by the object. context A collection of bindings of names to values. context slot A data structure used to hold processor execution state within a domain. ix domain The entity which is activated by the kernel scheduler. Domains can be thought of a...

A distributed shared memory (DSM) system allows shared memory parallel programs to be executed on distributed memory multiprocessors. The challenge in building a DSM system is to achieve good performance over a wide range of shared memory programs without requiring extensive modifications to the source code. The performance challenge translates into reducing the amount of communication performed by the DSM system to that performed by an equivalent message passing program. This thesis describes four novel techniques for reducing the communication overhead of DSM, including: (i) the use of software release consistency, (ii) support for multiple consistency protocols, (iii) a multiple writer protocol, and (iv) an update timeout mechanism. Release consistency allows modifications of shared data to be handled via a delayed update queue, which masks network latencies. Providing multiple cons...