Signals,timers, and continuations for multithreaded user‐level protocols

Precise timing and asynchronous I/O are appealing features for many applications. Unix kernels provide such features on a per‐process basis, using signals to communicate asynchronous events to applications. Per‐process signals and timers are grossly inadequate for complex multithreaded applications that require per‐thread signals and timers that operate at finer granularity. To respond to this need, we present a scheme that integrates asynchronous (Unix) signals with user‐level threads, using the ARIADNE system as a platform. This is done with a view towards support for portable, multithreaded, and multiprotocol distributed applications, namely the CLAM (connectionless, lightweight, and multiway) communications library. In the same context, we propose the use of continuations as an efficient mechanism for reducing thread context‐switching and busy‐wait overheads in multithreaded protocols. Our proposal for integrating timers and signal‐handling mechanisms not only solves problems related to race conditions, but also offers an efficient and flexible interface for timing and signalling threads. Copyright © 2006 John Wiley & Sons, Ltd.     

The Impact of Speculative Execution on SMT Processors

By executing two or more threads concurrently, Simultaneous MultiThreading (SMT) architectures are able to exploit both Instruction-Level Parallelism (ILP) and Thread-Level Parallelism (TLP) from the increased number of in-flight instructions that are fetched from multiple threads. However, due to incorrect control speculations, a significant number of these in-flight instructions are discarded from the pipelines of SMT processors (which is a direct consequence of these pipelines getting wider and deeper). Although increasing the accuracy of branch predictors may reduce the number of instructions so discarded from the pipelines, the prediction accuracy cannot be easily scaled up since aggressive branch prediction schemes strongly depend on the particular predictability inherently to the application programs. In this paper, we present an efficient thread scheduling mechanism for SMT processors, called SAFE-T (Speculation-Aware Front-End Throttling): it is easy to implement and allows an SMT processor to selectively perform speculative execution of threads according to the confidence level on branch predictions, hence preventing wrong-path instructions from being fetched. SAFE-T provides an average reduction of 57.9% in the number of discarded instructions and improves the instructions per cycle (IPC) performance by 14.7% on average over the ICOUNT policy across the multi-programmed workloads we simulate. This paper is an extended version of the paper, “Speculation Control for Simultaneous Multithreading,” which appeared in the Proceedings of the 18th International Parallel and Distributed Processing Symposium, Santa Fe, New Mexico, April 2004.     

基于VC++ 6.0的多串口通信方法

介绍了实现多串口通信的基本方法,采用VC 6.0并结合定时器和多线程技术编写,提出了实现多串口通信的三种方法,给出了实现的方法和步骤,并对三种方法进行了比较.实践证明,这三种模型均有效地实现了多串口通信.     

磁敏测速系统的数据采集平台实现

串口同步采集是工业控制应用的重要环节,为克服由于不准确的数据采集所带来的乘性误差,进而对多串口的同步采集进行了研究。利用VS2005编程环境,设计实现了多串口的上位机数据采集平台,该平台开辟线程对多个串口采取重叠读取方式,实现了对测速系统中大量的串口数据同步读取、保存并实现波形动态显示的功能,满足了智能测速系统的测速算法研究的需要。此平台可以广泛的应用在测速系统之中,也可辅助用于各种工业控制的高级要求。     

基于PCI总线的多功能可定制数据采集系统

为满足航空电子总线数据采集系统的通用性和多功能性,设计了基于PCI总线的多功能可定制数据采集系统;研究了相关总线板卡的驱动函数;采用自顶向下和模块化的方法设计了数据采集系统的系统运行管理模块、数据采集显示模块、数据分析处理模块和记录数据管理模块;使用了多线程、多视图、双缓存和Teechart控件等关键技术.设计实现的数...     

一种基于Web的远程监测系统实施方案的设计与实现

系统数据的实时性更新及其操作的方便程度是衡量监控系统软件优劣的重要因素。本文提出了一种基于Web的远程监测系统实施方案,软件体系采用集成了多线程和ActiveX控件等技术的C/S和B/S混合架构模式,克服了传统单一C/S模式的诸多缺点,使系统兼有了对内实时数据操作快速安全,对外信息发布与资源共享方便的性能;硬件环境采用基于虚拟串口技术的RS-485网络,使得监控系统底层网络可借助于企业Intranet,消除了总线竞争,提高了系统的实时性。     

网络教室管理系统中多媒体通信技术的应用

开发新的网络教室管理系统，对网络层次中底层TCP／IP协议进行了研究，论述了利用TCP、UDP协议实现网络通信的工作原理及其多线程的技术方法，并用流式传输的方法实现了网络教室中的多媒体信息高效实时的传输。     

摩托车耐久性试验台精确延时的实现

分析了对摩托车耐久性试验台控制系统软件开发中适时任务的特点，提出了采用可编程定时／计数器8253和系统时钟实现精确延时的方法，并采用了多线程技术避免了软件延时带来的负面影响．这种延时方法在摩托车耐久性试验台系统软件的开发中得以应用实现，收到了良好的控制效果．     

线程级并行计算在图形渲染引擎中的研究

针对并行计算技术在当前图形渲染系统中应用层面较浅的问题,为提高多核平台下图形应用程序CPU利用率,提出了一种新的Fork-Join多线程渲染方案。对当前流行的开源图形渲染引擎——OGRE引擎的渲染框架进行了多线程优化,用OpenMP方法对图形引擎的逻辑帧实现并行化,根据Win32线程库和DirectX11的多线程支持提出了一种渲染帧并行化方法,并将其应用于图形引擎。在多核平台上的实验结果表明,该方案能有效提高渲染速率和CPU利用率,改善CPU负载均衡。     

串口通信在CAD/CAM系统中的设计与实现

串行口通信是终端与计算机或计算机之间进行数据通信的一种方式，在工业上发挥着重要的作用。具有传输距离远、传输稳定、简单实用等特点。论述了在三维造型软件平台上(JHSolid)的CAM模块中串口通讯的实现。应用VisuaI C 结合CSem aJPort类实现自动侦测串口、在数控机床与PC之间进行数据及文件的传输等功能，并讨论该系统的基本原理和具体实现。