用户级实时线程的设计与实现

连续媒质的应用程序要求有实时线程高效灵活的支持,包括对线程属性的动态管理和多线程模式的支持。本文介绍在RT-Mach微内核上用户实时线程的设计和实现。     

FILiC:一种CUDA上的交互型库函数框架

CUDA是NVIDIA公司推出的GPU编程模型,它为高效利用GPU计算能力提供了强大的支持。但CUDA线程无法直接访问I/O设备、网卡等外围设备,在CUDA线程与外围设备的交互功能方面,目前CUDA的支持十分有限,仅支持非实时的屏幕打印(printf)。因此提出了一种交互型库函数框架FILiC,它通过设备和主机之间的巧妙交互,高效实现了CUDA线程实时的较完整I/O等函数;并且该框架具有很好的可扩展性,CUDA程序员或者编译器开发者可基于该框架按需求开发新的CUDA线程交互功能。     

不同操作系统下实现实时任务的比较

针对计算机实时控制系统对实时性，本文讨论了不同的操作系统环境对实时任务的处理和支持并着重讨论了利用线程提高实时性和实现时任务的方法。     

实时线程库研究与实现

并发已经日益成为当今软件的一个重要方面。该文力图通过实现一个高级的面向对象的,跨平台的C++线程和同步库,提供本地线程机制的高层抽象,从而获得更多的灵活性和控制性。特别是,针对实时系统中的优先级和调度的基本需求,开发了线程库的实时特性,实现了线程的本地优先级映射和支持优先级继承协议的锁机制。     

线程库的研究与实现

本文详细论述了分布式中间件和分布式应用开发对线程库的需求,并结合实时CORBA中间件开发的实际,提出了一个具有Java风格的线程接口、统一线程优先级、能够在不同平台上运行、具有多级调度能力、满足分时和实时应用的面向对象线程库;给出了线程库中关键技术的解决方法和相关算法。     

实时操作系统ThreadX剖析

ThreadX是—个成熟的商用强实时嵌入式操作系统，被广泛应用于消费电子、航空航天、通信与医疗等应用领域中。通过对ThreadX所提供的服务与开发组建、线程调度算法、线程同步与通信机制、中断服务以及多处理器支持等方面的分析，可知ThreadX以轻量级的规模，提供了良好的实时性、可靠性与易用性，是嵌入式应用中一个不错的RTOS选择。     

实时操作系统ThreadX剖析

ThreadX是一个成熟的商用强实时嵌入式操作系统,被广泛应用于消费电子、航空航天、通信与医疗等应用领域中.通过对ThreadX所提供的服务与开发组建、线程调度算法、线程同步与通信机制、中断服务以及多处理器支持等方面的分析,可知ThreadX以轻量级的规模,提供了良好的实时性、可靠性与易用性,是嵌入式应用中一个不错的RTOS选择.     

实时CORBA线程研究与实现

近年来实时CORBA的在金融、电信、保险、医疗、制造业等行业发挥着越来越重要的作用,开发基于实时CORBA的应用程序,提高系统端对端的预测能力,使系统具有可靠健壮的性能.首先论述了实时CORBA体系结构与线程控制机制,对实时CORBA的ORB、POA与线程控制机制关系、实时CORBA线程的实现方式、线程的管理策略作了分析讨论,在这基础上讨论了建立实时系统的应用实例,将CORBA优先映射为本地优先,提供了灵活的线程管理机制,有效防止了线程的优先级翻转.     

用户级线程

核心线程是微内核操作系统Ｍａｃｈ调度的基本单位，它较好地支持了细粒度的并行计算，但核心线程在支持用户并发模型、双并发模型上还有许多缺点。用户级线程是在核心线程的支持下建立的更高层次的用户调度单位，能较好地支持用户程序的并发执行。本文重点介绍在核心线程支持下的用户级线程—ＣＴｈｒｅａｄ的实现方案     

C#中利用多线程技术实现数据的实时测量

对于计算机实时测量系统,通常要求能够同时处理多个任务。文章介绍了在.NET Framework2.0环境下,利用C#编程语言,采用多线程技术的实时测量方法。C#编程语言中的Thread类用于对线程的操作,包括线程的创建和启动、控制线程的执行和线程之间的同步。在设计实例中给出了数据测量模块和测量线程的创建和启动代码。用户根据实际情况加入自己的测量代码,即可完成数据的实时测量工作。     

Coping with Java threads

A thread is a basic unit of program execution that can share a single address space with other threads - that is, they can read and write the same variables and data structures. Originally, only assembly programmers used threads. A few older programming languages such as PL/I supported thread concurrency, but newer languages such as C and C++ use libraries instead. Only recently have programming languages again begun to build in direct support for threads. Java and Ada are examples of industry-strength languages for multithreading. The Java thread model has its roots in traditional concurrent programming. As the "real-time specification for Java" sidebar describes, RTSJ attempts to remove some of the limitations relative to real-time applications - primarily by circumventing garbage collection. But RTSJ does not make the language safer. It retains standard Java's threading pitfalls and is a risky candidate for critical concurrent applications.     

Predictable threads for dynamic, hard real-time environments

Next-generation, hard real-time systems will require new, flexible functionality and guaranteed, predictable performance. This paper describes the UMass Spring threads package, designed specifically for multiprocessing in dynamic, hard real-time environments. This package is unique because of its support for new thread semantics for real-time processing. Predictable creation and execution of threads is achieved because of an underlying predictable kernel, the UMass Spring kernel. Design decisions and lessons learned while implementing the threads package are presented. Measurements affirm the predictability of this implementation on a representative multiprocessor platform. The adoption of the threads package in the UMass Spring kernel results in additional performance improvements, which include reduced context switching overhead and reduced average-case memory access durations     

Scheduling and admission testing for jitter-constrained periodic threads

We present new admission tests for periodic real-time threads with explicitly stated deadlines scheduled according to the earliest deadline first (EDF) algorithm. In traditional real-time periodic scheduling, the deadline of a periodic thread is conventionally the end of the current period. In contrast, our tests support periodic threads in which the deadline may be earlier than the end of the current period. In the extreme case, the deadline may be specified as identical to the per period execution time, which results in perfectly isochronous periodic threads. The provision of such threads, which we refer to as jitter-constrained threads, helps end-systems to honour jitter as well as throughput-related QoS parameters in distributed multimedia systems. In addition, such threads can reduce end-to-end delay and buffer memory requirements as less buffering is needed to smooth excessive delay jitter.     

Thread algebra for strategic interleaving

We take a thread as the behavior of a sequential deterministic program under execution and multi-threading as the form of concurrency provided by contemporary programming languages such as Java and C#. We outline an algebraic theory about threads and multi-threading. In the case of multi-threading, some deterministic interleaving strategy determines how threads are interleaved. Interleaving operators for a number of plausible interleaving strategies are specified in a simple and concise way. By that, we show that it is essentially open-ended what counts as an interleaving strategy. We use deadlock freedom as an example to show that there are properties of multi-threaded programs that depend on the interleaving strategy used. C. B. Jones     

信号实时采集系统的最佳并行线程数的研究

为解决多核环境下,信号采集系统的数据处理实时性问题,提高波形数据采集和数据显示速度,提出使用裸线程构建数据采集模块和数据处理模块的最佳线程分配数量的最优线程分配算法,其目的在于合理分配线程给各个模块,达到系统的最佳性能。该算法基于生产者-消费者模式、操作系统多线程时间片轮转调度策略,根据各模块的工作量酌情调节线程比例,使应用程序达到最高加速比。实验表明,在双核环境下,该最佳线程数算法计算出最佳线程组合,使采集波形数据和数据显示合理并行化,相对于其他的线程组合分配方式完成程序花费的时间更少,提高了系统加速比、运算性能以及实时性。通过最优线程分配算法,提供了最优的线程数量分配方案,提高并行程序执行效率,减少了不必要的线程开销,提高了波形信号采集实时性。     

利用软件线程集成技术实现硬件到软件的转移

该文介绍了线程集成，一种在通用单片微处理器或微控制器上低耗并行执行的新方法，后级编译技术有效地插入多个控制线程，并提供细粒度的多个线程而不用上下文切换的方法，这样允许用软件完成实时的功能来代替专用外围硬件。该文研究了在主线程中集成实时客户线程时的代码转移，生成的集成线程能满足所有的实时性，线程集成的概念和代码转移被应用到实际中来检验这种方法的可行性。     

应用于实时控制系统的线程池调度策略设计

在进行多任务实时控制系统设计时,采用线程池技术是一种有效的解决方法,但必须首先避免超时的发生。为了降低线程完成的超时发生率,采用Half-Sync/Half-Async线程池架构建立实时控制系统的线程池,利用最小二乘支持向量回归机（LSSVR）对线程执行时间进行预测估计,再基于估计结果对线程池线程的分配调度优先级别算法进行设计。性能测试以无线图像传感器网络节点为对象对所设计的LSSVR线程池及其他线程池在不同状态下的超时发生率做了比较,结果表明在大多数应用情况下LSSVR线程池在抑制超时方面具有明显的优越性。     

冗余多线程结构的重命名寄存器配对共享分配策略

同时多线程处理器允许多个线程同时执行,一方面提高了处理器的性能,另一方面也为通过线程冗余执行来容错提供了支持.冗余多线程结构将线程复制成两份,二者独立执行,并比较结果,从而实现检错或者容错.冗余多线程结构主要采用ICOUNT调度策略来解决线程间资源共享问题.然而这种策略有可能造成"饥饿"现象,并降低处理器吞吐率.提出一...     

Distributed strategic interleaving with load balancing

In a previous paper, we developed an algebraic theory of threads, interleaving of threads, and interaction of threads with services. In the current paper, we assume that the threads and services are distributed over the nodes of a network. We extend the theory developed so far to the distributed case by introducing distributed interleaving strategies that support explicit thread migration and see to load balancing or capability searching by implicit thread migration. The extension to the distributed case provides insight into details of multi-threading that come up in a networked environment.