Using multi-threads to hide deduplication I/O latency with low synchronization overhead

Data deduplication, as a compression method, has been widely used in most backup systems to improve bandwidth and space efficiency. As data exploded to be backed up, two main challenges in data deduplication are the CPU-intensive chunking and hashing works and the I/0 intensive disk-index access latency. However, CPU-intensive works have been vastly parallelized and speeded up by multi-core and many-core processors; the I/0 latency is likely becoming the bottleneck in data deduplication. To alleviate the challenge of I/0 latency in multi-core systems, multi-threaded deduplication （Multi-Dedup） architecture was proposed. The main idea of Multi-Dedup was using parallel deduplication threads to hide the I/0 latency. A prefix based concurrent index was designed to maintain the internal consistency of the deduplication index with low synchronization overhead. On the other hand, a collisionless cache array was also designed to preserve locality and similarity within the parallel threads. In various real-world datasets experiments, Multi-Dedup achieves 3-5 times performance improvements incorporating with locality-based ChunkStash and local-similarity based SiLo methods. In addition, Multi-Dedup has dramatically decreased the synchronization overhead and achieves 1.5-2 times performance improvements comparing to traditional lock-based synchronization methods.

An HLA/RTI Architecture Based on Multi-thread Processing

In order to improve the real-time performance of the real-time HLA(high level architecture) in the application of massive data communication volume,multi-thread processing was adopted,thread pool structure was introduced into the system,different threads to handle corresponding message queues was utilized to respond different message requests.Furthermore,an allocation strategy of semi-complete deprivation of priority was adopted,which reduces thread switching cost and processing burden in the system,provided that the message requests with high priority can be responded in time,thus improves the system's overall performance.The design and experiment results indicate that the method proposed in this paper can improve the real-time performance of HLA in distributed system applications greatly.

Dynamically Translating Binary Code for Multi-Threaded Programs Using Shared Code Cache

mc211vm is a process-level ARM-to-x86 binary translator developed in our lab in the past several years. Currently, it is able to emulate singlethreaded programs. We extend mc211vm to emulate multi-threaded programs. Our main task is to reconstruct its architecture for multi-threaded programs. Register mapping, code cache management, and address mapping in mc2llvm have all been modified. In addition, to further speed up the emulation, we collect hot paths, aggressively optimize and generate code for them at run time. Additional threads are used to alleviate the overhead. Thus, when the same hot path is walked through again, the corresponding optimized native code will be executed instead. In our experiments, our system is 8.8X faster than QEMU （quick emulator） on average when emulating the specified benchmarks with 8 guest threads.

On Multi-Thread Crawler Optimization for Scalable Text Searching

Web crawlers are an important part of modern search engines.With the development of the times,data has exploded and humans have entered a“big data era”.For example,Wikipedia carries the knowledge from all over the world,records the realtime news that occurs every day,and provides users with a good database of data,but because of the large amount of data,it puts a lot of pressure on users to search.At present,single-threaded crawling data can no longer meet the requirements of text crawling.In order to improve the performance and program versatility of single-threaded crawlers,a high-speed multi-threaded web crawler is designed to crawl the network hyper-scale text database.Multi-threaded crawling uses multiple threads to process web pages in parallel,combining breadth-first and depth-first algorithms to control web crawling.The practice project is based on the Python language to achieve multi-threaded optimization network hyper-large-scale text database-Wikipedia book crawling method,the project is inspired by the article on the Wikipedia article in the Big Data Digest public number.

Research and Review on the Java Multi-thread Programming and Its Further Development Tendency

In this paper, we conduct research on the Java multi-thread programming and its further development tendency. Multithreading mechanisms can run several programs at the same time, make the program run effi ciency becomes higher that also can overcome the problem of basic traditional programming language design while its design is the key to the realization of the synchronous thread. Multithreading is a mechanism that allows concurrent execution of multiple instruction stream in the program, each instruction stream is called a thread, independent from each other between each other. Thread is also known as a lightweight process, it have independent execution and process control. Our research starts from the analysis of the corresponding mechanism to enhance the performance that is innovative and meaningful.

基于同步控制的人和机器人握手动力学仿真

为实现人和机器人握手运动的同步,提出了基于神经元振荡器同步控制的方法,并将此方法应用于人和机器人握手的研究中.同时,在分析现有神经元振荡器特性的基础上,设计了一种新的人和机器人握手的神经元振荡器,并将该神经元振荡器应用于同步控制方法中进行人和机器人握手的动力学仿真,仿真结果证明了该控制方法的有效性.

PIV技术在旋转流场测试中的应用

考虑旋转流场自身特点,结合PIV非接触全场测量的优势,介绍了相位平均技术的原理、使用方法以及效果,并分析了它的劣势。描述了流场旋转、激光频闪、图像采集三个独立过程的同步控制技术,给出了一种优化控制参数从而减少误差的方法。实验结果证明:在旋转流场PIV测试中,使用这两种方法可以有效地减少测量误差。

Reduction of distortion and improvement of efficiency for gridding of scattered gravity and magnetic data

This paper presents a reasonable gridding-parameters extraction method for setting the optimal interpolation nodes in the gridding of scattered observed data. The method can extract optimized gridding parameters based on the distribution of features in raw data. Modeling analysis proves that distortion caused by gridding can be greatly reduced when using such parameters. We also present some improved technical measures that use human- machine interaction and multi-thread parallel technology to solve inadequacies in traditional gridding software. On the basis of these methods, we have developed software that can be used to grid scattered data using a graphic interface. Finally, a comparison of different gridding parameters on field magnetic data from Ji Lin Province, North China demonstrates the superiority of the proposed method in eliminating the distortions and enhancing gridding efficiency.

船舶推进器叶梢部流动PIV测试

利用2D-PIV(particle image velocimetry)技术在空泡水筒中对螺旋桨叶梢部流场进行了详细的测量。选用松花粉为示踪粒子,通过驱动轴轴编码器输出相位信号,经同步控制器控制CCD摄像及两激光器出光,解决了螺旋桨相位、激光器与CCD三者的同步控制与连续采集问题。轴向平面每一相位下均测量获得100幅瞬时速度矢量场,采用相位平均方法获得了同一相位下的平均速度场。比对了叶梢附近桨盘面前后流动的差异以及沿径向叶梢内外流场的不同,利用测试数据研究了梢涡、尾涡的结构。

基于PLC的复合胶条生产过程的自动控制

针对复合胶条的生产线,设计了以西门子S7-200PLC为核心的控制系统。PLC输出模拟量控制变频器的频率以实现多台电机的同步控制,胶条的垂度由光电开关检测,PLC内部控制算法保证胶条的垂度在一定范围内。该系统操作方便,可靠性高,得到了实际应用。

基于LabVIEW的机房互动教学系统设计

基于LabVIEW设计了机房互动教学系统,实现了PI教学法在机房教学中的应用,并增加了教学实用功能——上课签到和课后评价。利用LabVIEW中多线程与同步控制和状态机等关键技术,解决一对多网络通信问题,实现了教师与学生的实时互动。该系统不仅对于PI教学法的普及、教学改革具有积极的实践意义,且对基于虚拟仪器平台的应用程序开发具有参考价值。

大阵面天线自动展开与折叠技术研究与实现

介绍了一种大型阵面天线的自动展开和折叠的实现方法,描述了大阵面展开系统的原理及组成,并介绍了折展机构设计、自动展开撤收控制等关键技术。该大型天线自动展开撤收装置已成功应用于某地面雷达,通过使用验证,性能良好,可靠性高。

广州凤凰三桥拱肋整体提升技术

介绍广州凤凰三桥拱肋整体提升中运用的施工技术、临时结构的设计与提升控制。在方案设计实施过程中采取了主动控制提升架上拔力、主动控制下吊点张拉索力等技术措施,使得结构在运输、提升、卸载的不同阶段下受力可控;同步提升采取了高精度的位移、载荷控制技术,实现施工全过程控制与调整,确保结构受力合理,安装到位后满足设计要求受力状态。

双履带机器人电液行走控制系统建模与仿真

根据光伏板清扫机器人作业工况特点,提出了一种全液压履带式双阀控双马达驱动系统方案。为满足机器人直线行驶需求,提出双通道等同式交叉耦合同步控制策略,并建立阀控双马达同步控制系统数学模型。利用仿真工具Simulink对原设计系统模型和PID矫正后系统的动态特性性能进行仿真分析。仿真结果表明:校正后系统响应速度和稳定精度得到改善,经校正后,该系统能较好地满足清扫机器人工况要求。

Panoramic Imaging System Inspired by Insect Compound Eyes

Inspired by the unique structure of insect compound eyes,a multi-channel image acquisition system is designed to photograph a cylindrical panorama of its surroundings with one shot. The hardware structure consists of an embedded ARM system and one array of 16 micro-image sensors. The system achieves the synchronization of captured photos in 10 ms,as well as 10 f /s video capture. The software architecture includes the TCP /IP protocol,video capture procedures in"Poll/Read"or"video streaming"modes,thread pool monitoring in multi-threading mutex,synchronization control with the"event""mutex signal"and"critical region"functions,and a synthetic image algorithm characterized by its portability,modularity,and remote transmission. The panoramic imaging system is expected to be a vision sensor for mobile robotics.

基于滑模控制的作动器研究

为有效地消除船甲板由于发动机或螺旋桨不平衡矩所引起的振动,研制了一种新型作动器,其激振频率及激励力幅值均可实现在线调节,由于这种激励幅值的在线调节,使得整个系统的控制方程为非线性,为了消除控制系统参数变化和外部扰动对其跟踪性能的影响,将滑模控制引入其伺服跟踪控制,同时为了减小滑模控制器的颤抖采用了基于趋近律的位置及速度跟踪.仿真及实验结果表明滑模控制器具有较强的鲁棒性和跟踪性能,能有效地控制船甲板的振动.

Fault Detection and Isolation for Low Hardware Redundancy Flight Control System

The problems of current highly redundant flight control system are analyzed in this paper. Our study gives methods of utilizing other information to reduce physical components on the condition of meeting the reliability requirements for flight control system. The strategies presented in this paper mainly include information redundancy, multi-thread, time redundancy, geometry space redundancy, etc.. Analysis and simulation show these non-hardware based methods can reduce the requirement of system hardware level and thus reduce the system complexity, weight, space, costs and R＆D （research and development） time.

Improved Software Implementation for Montgomery Elliptic Curve Cryptosystem

The last decade witnessed rapid increase in multimedia and other applications that require transmitting and protecting huge amount of data streams simultaneously.For such applications,a high-performance cryptosystem is compulsory to provide necessary security services.Elliptic curve cryptosystem(ECC)has been introduced as a considerable option.However,the usual sequential implementation of ECC and the standard elliptic curve(EC)form cannot achieve required performance level.Moreover,the widely used Hardware implementation of ECC is costly option and may be not affordable.This research aims to develop a high-performance parallel software implementation for ECC.To achieve this,many experiments were performed to examine several factors affecting ECC performance including the projective coordinates,the scalar multiplication algorithm,the elliptic curve(EC)form,and the parallel implementation.The ECC performance was analyzed using the different factors to tune-up them and select the best choices to increase the speed of the cryptosystem.Experimental results illustrated that parallel Montgomery ECC implementation using homogenous projection achieves the highest performance level,since it scored the shortest time delay for ECC computations.In addition,results showed thatNAF algorithm consumes less time to perform encryption and scalar multiplication operations in comparison withMontgomery ladder and binarymethods.Java multi-threading technique was adopted to implement ECC computations in parallel.The proposed multithreaded Montgomery ECC implementation significantly improves the performance level compared to previously presented parallel and sequential implementations.

The Double Edge Sword Based Distributed Executor Service

Scalability is one of the most important quality attribute of softwareintensive systems,because it maintains an effective performance parallel to the large fluctuating and sometimes unpredictable workload.In order to achieve scalability,thread pool system(TPS)(which is also known as executor service)has been used extensively as a middleware service in software-intensive systems.TPS optimization is a challenging problem that determines the optimal size of thread pool dynamically on runtime.In case of distributed-TPS(DTPS),another issue is the load balancing b/w available set of TPSs running at backend servers.Existing DTPSs are overloaded either due to an inappropriate TPS optimization strategy at backend servers or improper load balancing scheme that cannot quickly recover an overload.Consequently,the performance of software-intensive system is suffered.Thus,in this paper,we propose a new DTPS that follows the collaborative round robin load balancing that has the effect of a double-edge sword.On the one hand,it effectively performs the load balancing(in case of overload situation)among available TPSs by a fast overload recovery procedure that decelerates the load on the overloaded TPSs up to their capacities and shifts the remaining load towards other gracefully running TPSs.And on the other hand,its robust load deceleration technique which is applied to an overloaded TPS sets an appropriate upper bound of thread pool size,because the pool size in each TPS is kept equal to the request rate on it,hence dynamically optimizes TPS.We evaluated the results of the proposed system against state of the art DTPSs by a clientserver based simulator and found that our system outperformed by sustaining smaller response times.

Error Robust H.264 Video Transmission Schemes Based on Multi-frame

Multi-frame coding is supported by the emerging H.264. It is important for the enhancement of both coding efficiency and error robustness. In this paper, error resilient schemes for H.264 based on multi-frame were investigated. Error robust H.264 video transmission schemes were introduced for the applications with and without a feedback channel. The experimental results demonstrate the effectiveness of the proposed schemes.