一种改进的进程调度算法在机顶盒上的设计与实现

调度算法对操作系统中的实时性起着关键的作用.就此问题,深入分析了基于最小优裕度算法的内核进程调度算法,为更好地满足Linux系统对嵌入式系统实时可靠性的要求,对现有的LSF调度策略进行分析,指出LSF算法调度算法的不足.为了改进LSF算法的颠簸现象,基于抢占阈值的思想,提出适用于LSF算法的抢占阈值分配方法,动态地给每...     

嵌入式Linux2.6的实时性能研究与优化

以Linux2.6内核为对象,对Linux系统实时性进行了研究.针对Linux中时钟粒度过大、临界区的执行造成系统反应延迟的不确定性和进程调度算法在任务调度过程中的公平性体现不够等,提出根据实时应用的特点设计了一个并行高精度定时器以提高时钟精度;采用自旋锁双模块控制方式对临界区进行管理以减少时延;修改0(1)调度算法的双队列操作,同时增加时间片轮询装置和采用动态计算通用进程的优先级和时间片的方法以提高调度的公平性和系统快速响应时间.实验测试表明:改进方案有效提高了系统的实时性,扩充了Linux在嵌入式领域的应用性.     

虚拟CPU负载预测算法性能评估

准确的虚拟CPU负载预测是提高虚拟机CPU调度性能的重要前提,然而,虚拟机操作系统环境下,虚拟CPU负载预测方法需要尽可能简单、有效.针对虚拟机CPU调度应用场景,以实际CPU负载为研究对象,选取五种简单的时间序列预测算法,详细评估其虚拟CPU负载预测性能,为虚拟机CPU调度的实现提供了研究基础.结果表明,平均移动法、...     

操作系统调度算法的研究

操作系统是管控计算机软硬件资源的基础软件,现代操作系统很多都是多任务系统,操作系统需要解决多任务间的合理调度、分配运行资源等重要问题。文章介绍了操作系统调度算法的分类和选择准则,并分析研究了几种经典的操作系统调度算法,对它们的优缺点和适用场合进行了介绍,为调度算法的深入研究提供了借鉴。     

基于多线程的进程调度演进过程的仿真设计

操作系统涉及计算机系统中各种软,硬件资源的管理,概念抽象,各种资源管理的算法复杂。文章针对WINDOWS操作系统进程调度演进过程进行了仿真设计。系统运用了JAVA多线程机制,完成不同进程调度算法演进过程的仿真、数据记录和分析;进程参数设置具有随机性;系统可视化描述进程的动态性。     

Linux的进程调度策略

随着Linux操作系统在嵌入式系统方面的应用越来越广泛,关于增强并改进Linux对实时任务支持方面的研究也越来越多.该文通过对Liunx下进程调度的原理、依据以及调度算法、实时调度策略的全面分析,说明了Linux对普通进程和实时进程进行相应处理的过程.同时为了改进Linux对实时任务的支持,提出了一种混合调度算法.     

高速无线个域网中一种基于效用公平的机会调度算法

基于对无线高速个域网中机会调度的研究,提出了一种适用于WPAN的机会主义时隙调度算法FPTS。该算法充分考虑了信道状态的波动和用户间的公平性,由参数更新模块和调度分配模块组成。参数更新模块根据调度结果更新控制参数,维护用户的公平性和自适应的跟踪信道的变化;调度分配模块负责计算每个用户的公平效用权值,并按照权值向各用户比例分配信道资源。仿真结果表明：所提调度方案能够在保证系统高吞吐量的前提下,获得LLPTS算法更好的公平性和信道使用效率。     

MIMO无线通信系统中调度算法分析

对轮询算法、最大载干比算法和比例公平算法三种经典的调度算法进行了深入的研究,并在MIMO系统环境中,对它们的性能进行了计算机仿真。从基本原理和仿真结果两个方面,对上述三种调度算法的公平性和系统吞吐量性能进行了对比分析,证明了轮询算法具有最好的公平性性能,最大载干比算法具有最好的吞吐量性能,比例公平算法则很好的在两者之间取得了一个平衡。     

感知无线电中频谱共享技术的研究

文章研究了感知无线电网络中联合频谱分配和调度的问题,给出了基于物理干扰模型的频谱分配算法。调度算法是对由频谱分配算法得到的一系列传输模式进行调度,从而实现频谱共享。本文基于提出的频谱分配算法通过仿真比较了三种调度算法,结果表明考虑了公平性的调度算法的网络吞吐量有稍微的降低（可达到最大吞吐量的96%）,但感知用户的整体需求满足度却得到了很大的提高,即达到了很好的公平性。     

进程调度策略在Linux中的实现

Linux是一个多用户多任务的操作系统。系统上所有运行的东西都可以称作进程。Linux把进程分为实时进程和非实时进程来处理,它采用时间片轮转和可剥夺调度优先级相结合的调度策略。详细介绍了实时进程和非实时进程在Linux不同进程调度中的应用。     

A UNIFYING QUEUEING MODEL FOR ATM AND ITS ANALYSIS

This paper considers a discrete-time single-server queueing system with infinite buffer size and a finite number of independent Markov-modulated Bernoulli processes (MMBPs). A simple analytical approach is presented to analyse the asymptotic behaviour of such a queueing system. An explicit expression for the tail distribution of the buffer contents is given, from which two upper bounds for the tail distribution are derived. These two upper bounds are good and even tight in many cases, as shown by the numerical results. Compared to a previously reported general solution technique, our approximate analytical approach is very easy to use and is not limited by the system size and the traffic parameters. The CPU time required to calculate the upper bounds of the tail distribution is quite acceptable for practical use; especially for a single traffic type, the calculation costs nearly no CPU time on a normal PC. This analytical method is also suitable for more general Markov-modulated arrival processes.     

一种高效的硬布线控制CPU的设计方法

文章提出了一种硬布线逻辑CPU的设计流程，即以CPU设计工具软件LDF为核心的设计方法，其主要目的的提高硬布线逻辑CPU的设计效率。定义了一种用于描述硬布线控制逻辑的语言-MCDL，对总线优化问题进行了研究，并且给出了解决总线优化问题的近似算法。     

字符串匹配算法的实现:CPU vs.GPU vs.FPGA

针对字符串匹配算法在各平台实现的性能问题,将算法在CPU、GPU及FPGA上做了测试对比。GPU具有计算单元多的特点,使得GPU对计算密集型应用有较大的效率提升;而FPGA具有级强的灵活性、可编程性及大量的逻辑运算单元,在处理字符串匹配时的处理速度快。通过对3种实现方式在Snort规则库下做的分析,其结果表明,FPGA的处理速度最快,相比GPU的处理速度提升了10倍。而CPU的串行处理速度最慢,且FPGA的资源消耗最多,GPU次之,CPU的资源消耗最少,且实现最简单。     

基于改进遗传算法的服务器端负载均衡算法

在负载均衡技术中，负载调度方法是核心，它的好坏直接影响均衡系统的性能。提出一种基于改进遗传算法的服务器端负载均衡算法。该方法降低了服务器端请求的响应时间。提高了服务器端CPU的利用率。从而改善了系统性能。数据实例表明。该方法是可行的、正确的和有效的。     

超标量RISC微处理器指令发射算法设计

提出了一种基于分布式控制方式的动态指令调度算法,该算法能够有效提高指令发射效率,降低指令分派单元逻辑复杂度,提高系统主频.该指令发射算法在自主设计的"龙腾R3" RISC"三发射"超标量微处理器中进行应用实现,达到了设计预期目标.     

A Petri Net Method for Schedulability and Scheduling Problems in Single-Arm Cluster Tools With Wafer Residency Time Constraints

With wafer residency time constraints for some wafer fabrication processes, such as low pressure chemical–vapor deposition, the schedulability and scheduling problems are still open. This paper aims to solve both problems. A Petri net (PN) model is developed for the system. This model describes when the robot should wait and a robot wait is modeled as an event in an explicit way. Thus, to schedule a single-arm cluster tool with wafer residency time constraint is to decide how long a robot wait should be. Based on this model, for the first time, we present the necessary and sufficient conditions under which a single-arm cluster tool with residency time constraints is schedulable, which can be checked analytically. Meanwhile, a closed form scheduling algorithm is developed to find an optimal periodic schedule if it is schedulable. Also, a simple method is presented for the implementation of the periodic schedule for steady state, which is not seen in any previous work.      

A maintenance inspection model for a single machine with general failure distribution

In this paper we develop a mathematical model for determining a periodic inspection schedule in a preventive maintenance program for a single machine subject to random failure. We formulate the problem as a profit maximization model with general failure time distribution. We show that under certain conditions on the probability density function of failure, a unique optimal inspection interval can be obtained. When the failure times are exponentially distributed, we propose alternative optimal and heuristic procedures to find exact and approximate inspection intervals. Our heuristic solution method is shown numerically to be more efficient than an earlier published heuristic procedure. We also investigated the sensitivity of the optimal inspection interval and expected profit per unit of time with respect to the changes in the two parameters of the Weibull time to failure distribution.     

Optimal Design and Control of CPU Heat Sink Processes

This paper considers the optimal plate fin design and control for central processing unit (CPU) heat sink processes. First, we apply a finite element method to investigate the heat transfer phenomena of a heat sink process. To have a better heat dispersion performance, a real-coded genetic algorithm is then utilized to search for an optimal set of plate-fin shape parameters. The objective function to be minimized is the entropy generation rate which can take simultaneously the two major factors, heat transfer rate and air resistance, into consideration in the design. The present optimization scheme is able to achieve a better design for heat dispersion than existing methods. To attenuate environmental and time-varying disturbances, a direct adaptive control scheme is then developed for the CPU heat sink process. It is based on using a bounded single neuron controller (SNC) along with a parameter tuning algorithm to regulate the temperature of a selected control point. Extensive comparisons of the SNC-based control performance with the on-off control as well as a PI controller show that the proposed scheme provides excellent control performance despite the existence of unexpected process uncertainties.     

Analyzing electromagnetic structures with curved boundaries onCartesian FDTD meshes

In this paper, a new finite-difference time-domain (FDTD) algorithm is investigated to analyze electromagnetic structures with curved boundaries using a Cartesian coordinate system. The new algorithm is based on a nonorthogonal FDTD method. However, only those cells near the curved boundaries are calculated by nonorthogonal FDTD formulas; most of the grid is orthogonal and can be determined by traditional FDTD formulas. Therefore, this new algorithm is more efficient than general nonorthogonal FDTD schemes in terms of computer resources such as memory and central processing unit (CPU) time. Simulation results are presented and compared to those using other methods     

A Recovery Algorithm of Linear Complexity in the Time-Domain Layered Finite Element Reduction Recovery (LAFE-RR) Method for Large-Scale Electromagnetic Analysis of High-Speed ICs

Time-domain layered finite element reduction recovery (LAFE-RR) method was recently developed for large-scale electromagnetic analysis of high-speed integrated circuits (ICs). This method is capable of analytically and rigorously reducing the system matrix of a 3-D multilayer circuit to that of a single-layer one regardless of the original problem size. In addition, the reduced system matrix preserves the sparsity of the original system matrix. In this paper, an efficient algorithm is proposed to recover the volume unknowns in the time-domain LAFE-RR method. This algorithm constitutes a direct solution of the matrix formed by volume unknowns in each layer. This direct solution possesses a linear complexity in both central processing unit (CPU) time and memory consumption. The cost of matrix inversion is negligible. The cost of matrix solution scales linearly with the matrix size. Numerical and experimental results have demonstrated the accuracy and efficiency of the proposed algorithm.