Individual machines are no longer sufficient to handle the offered load to many Internet sites. To use multiple machines for scalable performance, load balancing, fault transparency, and backward compatibility with URL naming must be addressed. A number of approaches have been developed to provide transparent access to multi-server Internet services includingHTTP redirect, DNS aliasing, Magic Routers, and Active Networks. Recently however, portable Java code and lightly loaded client machines allow the migration of certain service functionality onto the client. In this paper, we argue that in many instances, a client-side approach to providing transparent access to Internet services provides increased flexibility and performance over the existing solutions. We describe the design and implementation of Smart Clients and show how our system can be used to provide transparent access to scalable and/or highly available network services, including prototypes for: telnet, FTP, and an Internet chat application. 1

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Modern commodity operating systems are large and complex systems developed over many years by large teams of programmers, containing hundreds of thousands of lines of code. Consequently, it is extremely difficult to add significant new functionality to these systems. In response to this problem, a number of recent research projects have explored novel operating system architectures to support untrusted extensions, including SPIN, VINO, Exokernel, and Fluke. Unfortunately, these architectures require substantialimplementation effort and are not generally available in commodity systems. In contrast, by leveraging the technique of interposition, we have designed and implemented a prototype extension system called SLIC which requires only trivial operating system

ions To provide remote execution of both parallel and sequential jobs, GLUnix extends some existing UNIX abstractions and introduces new abstractions, borrowing heavily from MPP environments such as that of the CM-5. The new abstractions include network programs and globally unique network program identifiers (NPIDs) for GLUnix jobs and virtual node numbers (VNNs) to name the nodes running a network program. The existing abstractions of signal delivery to remote applications and I/O redirection were extended to support parallel and remote jobs. GLUnix provides both programming and command-line interfaces to access these abstractions. Network Programs A network program is an executing parallel or sequential job that is controlled by GLUnix. Network programs can be located anywhere in the cluster and are identified using a 32-bit, cluster-unique network program identifier (NPID) which is assigned and tracked by GLUnix. Using a cluster-wide, location-independent identifier provides th...

Parallel Virtual Machine (PVM) is a widely-used software system that allows a heterogeneous set of parallel and serial UNIX-based computers to be programmed as a single distributed-memory parallel machine. In this paper, an extension to PVM to support dynamic process migration is presented. Support for migration is important in general-purpose workstation environments since it allows parallel computations to co-exist with other applications, using idle-cycles as they become available and off-loading from workstations when they are no longer free. A description and evaluation of the design and implementation of the prototype Migratable PVM system is presented together with some performance results. 1 Introduction PVM [1, 2, 3] is a software system that allows a heterogeneous network of parallel and serial computers to be programmed as a single computational resource. This resource appears to the application programmer as a potentially large distributed-memory virtual computer. Such a s...

In this paper, we describe the design of a system, called ParaWeb, for utilizing Internet or intra-net computing resources in a seamless fashion. The goal is to allow users to execute serial programs on faster compute servers or parallel programs on a variety of possibly heterogeneous hosts. ParaWeb provides extensions to the Java programming environment (through a parallel class library) and the Java runtime system that allow programmers to develop new Java applications with parallelism in mind, or to execute existing Java applications written using Java's multithreading facilities in parallel. Some experimental results from our prototype implementation are used to demonstrate the potential of this approach. 1 Introduction The recent explosion of the World-Wide Web has enabled a diverse set of new Internet related applications and technologies. Among the key attractions of the Web has been the promise of easy access to a wealth of information around the world. Currently, however, the...

A process is an operating system abstraction representing an instance of a running computer program. Process migration is the act of transferring a process between two machines during its execution. Several implementations

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Scheduling algorithms that use application and system knowledge have been shown to be more effective at scheduling parallel jobs on a multiprocessor than algorithms that do not. This paper focuses on obtaining such information for use by a scheduler in a network of workstations environment. The log files from three parallel systems are examined to determine both how to categorize parallel jobs for storage in a job database and what job information would be useful to a scheduler. A Historical Profiler is proposed that stores information about programs and users, and manipulates this information to provide schedulers with execution time predictions. Several preemptive and non-preemptive versions of the FCFS, EASY and Least Work First scheduling algorithms are compared to evaluate the utility of the profiler. It is found that both preemption and the use of application execution time predictions obtained from the Historical Profiler lead to improved performance.

In this paper, we present the design of Cilk-NOW, a runtime system that adaptively and reliably executes functional Cilk programs in parallel on a network of UNIX workstations. Cilk (pronounced “silk”) is a parallel multithreaded extension of the C language, and all Cilk runtime systems employ a provably efficient threadscheduling algorithm. Cilk-NOW is such a runtime system, and in addition, Cilk-NOW automatically delivers adaptive and reliable execution for a functional subset of Cilk programs. By adaptive execution, we mean that each Cilk program dynamically utilizes a changing set of otherwise-idle workstations. By reliable execution, we mean that the Cilk-NOW system as a whole and each executing Cilk program are able to tolerate machine and network faults. Cilk-NOW provides these features while programs remain fault oblivious, meaning that Cilk programmers need not code for fault tolerance. Throughout this paper, we focus on end-to-end design decisions, and we show how these decisions allow the design to exploit high-level algorithmic properties of the Cilk programming model in order to simplify and streamline the implementation.