386 research outputs found

    Effective interprocess communication (IPC) in a real-time transputer network

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    The thesis describes the design and implementation of an interprocess communication (IPC) mechanism within a real-time distributed operating system kernel (RT-DOS) which is designed for a transputer-based network. The requirements of real-time operating systems are examined and existing design and implementation strategies are described. Particular attention is paid to one of the object-oriented techniques although it is concluded that these techniques are not feasible for the chosen implementation platform. Studies of a number of existing operating systems are reported. The choices for various aspects of operating system design and their influence on the IPC mechanism to be used are elucidated. The actual design choices are related to the real-time requirements and the implementation that has been adopted is described. [Continues.

    Concurrency Platforms for Real-Time and Cyber-Physical Systems

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    Parallel processing is an important way to satisfy the increasingly demanding computational needs of modern real-time and cyber-physical systems, but existing parallel computing technologies primarily emphasize high-throughput and average-case performance metrics, which are largely unsuitable for direct application to real-time, safety-critical contexts. This work contrasts two concurrency platforms designed to achieve predictable worst case parallel performance for soft real-time workloads with millisecond periods and higher. One of these is then the basis for the CyberMech platform, which enables parallel real-time computing for a novel yet representative application called Real-Time Hybrid Simulation (RTHS). RTHS combines demanding parallel real-time computation with real-time simulation and control in an earthquake engineering laboratory environment, and results concerning RTHS characterize a reasonably comprehensive survey of parallel real-time computing in the static context, where the size, shape, timing constraints, and computational requirements of workloads are fixed prior to system runtime. Collectively, these contributions constitute the first published implementations and evaluations of general-purpose concurrency platforms for real-time and cyber-physical systems, explore two fundamentally different design spaces for such systems, and successfully demonstrate the utility and tradeoffs of parallel computing for statically determined real-time and cyber-physical systems

    Using Latency to Evaluate Computer System Performance

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    Building high performance computer systems requires an understanding of the behaviour of systems and what makes them fast or slow. In addition to our file system performance analysis, we have a number of projects in measuring, evaluating, and understanding system performances. The conventional methodology for system performance measurement, which relies primarily on throughput-sensitive benchmarks and throughput metrics, has major limitations when analyzing the behaviour and performance of interactive workloads. The increasingly interactive character of personal computing demands new ways of measuring and analyzing system performance. In this paper, we present a combination of measurement techniques and benchmark methodologies that address these problems. We use some simple methods for making direct and precise measurements of event handling latency in the context of a realistic interactive application. We analyze how results from such measurements can be used to understand the detailed behaviour of latency-critical events. We demonstrate our techniques in an analysis of the performance of two releases of Windows 9x and Windows XP Professional. Our experience indicates that latency can be measured for a class of interactive workloads, providing a substantial improvement in the accuracy and detail of performance information over measurements based strictly on throughput

    Design, Implementation, and Evaluation of a Distributed Real-Time Kernel for Distributed Robotics (Dissertation Proposal)

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    Modern robotics applications are becoming more complex due to greater numbers of sensors and actuators. The control of such systems may require multiple processors to meet the computational demands and to support the physical topology of the sensors and actuators. A distributed real-time system is needed to perform the required communication and processing while meeting application-specified timing constraints. We are designing and implementing a real-time kernel for distributed robotics applications. The kernel\u27s salient features are consistent, user-definable scheduling, explicit dynamic timing constraints, and a two-tiered interrupt approach. The kernel wi1l be evaluated by implementing a two-arm robot control example. Its goal is to locate and manipulate cylindrical objects with spillable contents. Using the application and the kernel, we will investigate the effects of time granularity, network type and protocol, and the handling of external events using interrupts versus polling. Our research will enhance understanding of real-time kernels for distributed robotics control

    Jiko kaifukugata operetingu shisutemu kochiku furemu waku

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    制度:新 ; 報告番号:甲2786号 ; 学位の種類:博士(工学) ; 授与年月日:2009/2/25 ; 早大学位記番号:新500

    The design and implementation of a prototype exokernel operating system

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    Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1996.Includes bibliographical references (p. 99-106).by Dawson R. Engler.M.S

    Replication and fault-tolerance in real-time systems

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    PhD ThesisThe increased availability of sophisticated computer hardware and the corresponding decrease in its cost has led to a widespread growth in the use of computer systems for realtime plant and process control applications. Such applications typically place very high demands upon computer control systems and the development of appropriate control software for these application areas can present a number of problems not normally encountered in other applications. First of all, real-time applications must be correct in the time domain as well as the value domain: returning results which are not only correct but also delivered on time. Further, since the potential for catastrophic failures can be high in a process or plant control environment, many real-time applications also have to meet high reliability requirements. These requirements will typically be met by means of a combination of fault avoidance and fault tolerance techniques. This thesis is intended to address some of the problems encountered in the provision of fault tolerance in real-time applications programs. Specifically,it considers the use of replication to ensure the availability of services in real-time systems. In a real-time environment, providing support for replicated services can introduce a number of problems. In particular, the scope for non-deterministic behaviour in real-time applications can be quite large and this can lead to difficultiesin maintainingconsistent internal states across the members of a replica group. To tackle this problem, a model is proposed for fault tolerant real-time objects which not only allows such objects to perform application specific recovery operations and real-time processing activities such as event handling, but which also allows objects to be replicated. The architectural support required for such replicated objects is also discussed and, to conclude, the run-time overheads associated with the use of such replicated services are considered.The Science and Engineering Research Council

    Using program behaviour to exploit heterogeneous multi-core processors

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    Multi-core CPU architectures have become prevalent in recent years. A number of multi-core CPUs consist of not only multiple processing cores, but multiple different types of processing cores, each with different capabilities and specialisations. These heterogeneous multi-core architectures (HMAs) can deliver exceptional performance; however, they are notoriously difficult to program effectively. This dissertation investigates the feasibility of ameliorating many of the difficulties encountered in application development on HMA processors, by employing a behaviour aware runtime system. This runtime system provides applications with the illusion of executing on a homogeneous architecture, by presenting a homogeneous virtual machine interface. The runtime system uses knowledge of a program's execution behaviour, gained through explicit code annotations, static analysis or runtime monitoring, to inform its resource allocation and scheduling decisions, such that the application makes best use of the HMA's heterogeneous processing cores. The goal of this runtime system is to enable non-specialist application developers to write applications that can exploit an HMA, without the developer requiring in-depth knowledge of the HMA's design. This dissertation describes the development of a Java runtime system, called Hera-JVM, aimed at investigating this premise. Hera-JVM supports the execution of unmodified Java applications on both processing core types of the heterogeneous IBM Cell processor. An application's threads of execution can be transparently migrated between the Cell's different core types by Hera-JVM, without requiring the application's involvement. A number of real-world Java benchmarks are executed across both of the Cell's core types, to evaluate the efficacy of abstracting a heterogeneous architecture behind a homogeneous virtual machine. By characterising the performance of each of the Cell processor's core types under different program behaviours, a set of influential program behaviour characteristics is uncovered. A set of code annotations are presented, which enable program code to be tagged with these behaviour characteristics, enabling a runtime system to track a program's behaviour throughout its execution. This information is fed into a cost function, which Hera-JVM uses to automatically estimate whether the executing program's threads of execution would benefit from being migrated to a different core type, given their current behaviour characteristics. The use of history, hysteresis and trend tracking, by this cost function, is explored as a means of increasing its stability and limiting detrimental thread migrations. The effectiveness of a number of different migration strategies is also investigated under real-world Java benchmarks, with the most effective found to be a strategy that can target code, such that a thread is migrated whenever it executes this code. This dissertation also investigates the use of runtime monitoring to enable a runtime system to automatically infer a program's behaviour characteristics, without the need for explicit code annotations. A lightweight runtime behaviour monitoring system is developed, and its effectiveness at choosing the most appropriate core type on which to execute a set of real-world Java benchmarks is examined. Combining explicit behaviour characteristic annotations with those characteristics which are monitored at runtime is also explored. Finally, an initial investigation is performed into the use of behaviour characteristics to improve application performance under a different type of heterogeneous architecture, specifically, a non-uniform memory access (NUMA) architecture. Thread teams are proposed as a method of automatically clustering communicating threads onto the same NUMA node, thereby reducing data access overheads. Evaluation of this approach shows that it is effective at improving application performance, if the application's threads can be partitioned across the available NUMA nodes of a system. The findings of this work demonstrate that a runtime system with a homogeneous virtual machine interface can reduce the challenge of application development for HMA processors, whilst still being able to exploit such a processor by taking program behaviour into account
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