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International Conference on parallel and distributed Systems (ICPADS)

作者： Liufeng Wang Huaimin Wang Lu Cai Rui Chu Pengfei Zhang Lanzheng Liu National Key Laboratory for Parallel and Distributed Processing National University of Defense Technology Changsha China School of Economics and Management Xi'an University Xi'an China

Increasing Internet business and computing footprint motivate server consolidation in data centers. Through virtualization technology, server consolidation can reduce physical hosts and provide scalable services. However, the ineffective memory usage among multiple virtual machines (VMs) becomes the bottleneck in server consolidation environment. Because of inaccurate memory usage estimate and the lack of memory resource managements, there is much service performance degradation in data centers, even though they have occupied a large amount of memory. In order to improve this scenario, we first introduce VM's memory division view and VM's free memory division view. Based on them, we propose a hierarchal memory service mechanism. We have designed and implemented the corresponding memory scheduling algorithm to enhance memory efficiency and achieve service level agreement. The benchmark test results show that our implementation can save 30% physical memory with 1% to 5% performance degradation. Based on Xen virtualization platform and balloon driver technology, our works actually bring dramatic benefits to commercial cloud computing center which is providing more than 2,000 VMs' services to cloud computing users.

关键词： Memory management Resource management Servers Scheduling algorithm Benchmark testing Cloud computing System performance

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Performance problems online detection in cloud computing systems via analyzing request execution paths

Performance problems online detection in cloud computing sys...

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International Conference on Dependable Systems and Networks Workshops (DSN-W)

作者： Haibo Mi Huaimin Wang Gang Yin Hua Cai Qi Zhou Tingtao Sun National Laboratory for Parallel and Distributed Processing National University of Defense Technology Changsha China Computing Platform Alibaba Cloud Computing Company Hangzhou China

It is quite a headache for developers to online detect performance problems in large-scale cloud computing systems. The behavior and the hidden connections among the huge amount of runtime request execution paths in cloud computing systems usually contain useful information for performance problem detection. In this paper, we propose an approach to rapidly diagnose the source of performance degradation in large-scale non-stop cloud computing systems. The approach first groups the user requests into categories with a fast clustering algorithm; then applies the principal components analysis to extract the primary methods; finally compares the normal and abnormal behaviors of the primary methods to localize the main cause of performance problems. We conduct extensive experiments over a real-world enterprise system providing services for the public. The results show that our approach can locate the prime causes of performance problems accurately and efficiently.

关键词： Cloud computing Principal component analysis Instruments Degradation Servers Data mining Accuracy

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Identifying faults in large-scale distributed systems by filtering noisy error logs

Identifying faults in large-scale distributed systems by fil...

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International Conference on Dependable Systems and Networks Workshops (DSN-W)

作者： Xiang Rao Huaimin Wang Dianxi Shi Zhenbang Chen Hua Cai Qi Zhou Tingtao Sun National Laboratory for Parallel and Distributed Processing National University of Defense Technology Changsha China Computing Platform Alibaba Cloud Computing Corporation Hangzhou China

Extracting fault features with the error logs of fault injection tests has been widely studied in the area of large scale distributed systems for decades. However, the process of extracting features is severely affected by a large amount of noisy logs. While the existing work tries to solve the problem by compressing logs in temporal and spatial views or removing the semantic redundancy between logs, they fail to consider the co-existence of other noisy faults that generate error logs instead of injected faults, for example, random hardware faults, unexpected bugs of softwares, system configuration faults or the error rank of a log severity. During a fault feature extraction process, those noisy faults generate error logs that are not related to a target fault, and will strongly mislead the resulted fault features. We call an error log that is not related to a target fault a noisy error log. To filter out noisy error logs, we present a similarity-based error log filtering method SBF, which consists of three integrated steps: (1) model error logs into time series and use haar wavelet transform to get the approximate time series; (2) divide the approximate time series into sub time series by valleys; (3) identify noisy error logs by comparing the similarity between the sub time series of target error logs and the template of noisy error logs. We apply our log filtering method in an enterprise cloud system and show its effectiveness. Compared with the existing work, we successfully filter out noisy error logs and increase the precision and the recall rate of fault feature extraction.

关键词： Time series analysis Noise measurement Feature extraction Wavelet transforms Computer crashes Complexity theory Approximation methods

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An effective control scheme to ensure real-time causal order in large-scale distributed interactive simulations

An effective control scheme to ensure real-time causal order...

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International Conference on Communication Software and Networks, ICCSN

作者： Hangjun Zhou Sha Fu Key Laboratory of Science and Technology for National Defence of Parallel and Distributed Processing School of Computer Science National University of Defense Technology Changsha Hunan China Department of Information Management Hunan University of Finance and Economics Changsha Hunan China

When a large-scale distributed interactive simulation system is running on WAN, the sites usually disperse over a wide area in geography, which results in the simulation clock of each site is hardly to be accurately synchronized with that of other sites. The asynchronous clocks and large transmission latency on WAN bring on a problem for the large-scale simulations to preserve the real-time causal order delivery of received events at each site. In this article, we analyze the indirect way to compare the values of asynchronous simulation clocks at first, and then propose a novel scheme which can select the reconstructible causal control information for each message so as to ensure the causal ordering of events in real time. Experiments demonstrate that the scheme can weaken the effect of network latency, reduce the overhead of the transmission amount of control information and improve the causal order consistency in asynchronous distributed simulations.

关键词： Clocks Educational institutions

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A causality based dynamic message ordering for DVEs on Wide Area Network

A causality based dynamic message ordering for DVEs on Wide ...

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International Conference on Communication Software and Networks, ICCSN

Due to the large message transmission latency in distributed Virtual Environments(DVEs) on Wide Area Net-work(WAN), the effectiveness of causality consistency control of message ordering is determined by not only causal order of messages but also the real-timeness. If merely causal order is considered, the real-time property of DVEs may not be ensured because of the unlimited waiting time for the delayed messages. While if only real-timeness is emphasized, there may be too many delayed messages, which have to be discarded, to maintain the quality of causal message ordering. Therefore, a trade-off between the quality of causal order delivery and real-timeness is necessary for DVEs. In this article, a novel causality based message ordering approach is presented. In general, this new approach dynamically balances the demands of causal order delivery and real-timeness. Experiment results demonstrate the approach can enhance the quality of causality, while simultaneously keep the real-time property of DVEs.

关键词： Educational institutions

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A skew angle detection algorithm based on maximum gradient difference

A skew angle detection algorithm based on maximum gradient d...

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2011 International Conference on Transportation, Mechanical, and Electrical Engineering, TMEE 2011

作者： Wang, Dan Wang, Xichang Liu, Jiang Institute of Information Science and Engineering Shandong Normal University Shandong Province Key Laboratory for Distributed Computer Software Novel Technology Shandong China Shandong Oumasoft Co. Ltd Research Institute of Digital Image Processing Shandong China

ISBN: (纸本)9781457717017

In order to resolve the problem of skew phenomenon in the handwritten document image during the scanning process, a new skew angle detection algorithm based on maximum gradient difference as well as Hough transform was proposed in the paper. Firstly, text lines are labeled by using maximum gradient difference, and then we use the method of non-text filtering to get rid of shorter text lines and dots. Finally, margin information is extracted after refining on text lines, and two-stage Hough transform is made to the margin extracted information with the strategy varying from "coarse" to "fine" strategy, calculating the skew angle of document image which is fixed by the average of several longest lines. Experiment results shows that the algorithm detects skew angles of document image more rapidly and accurately than Hough transform alone. © 2011 IEEE.

关键词： Hough transforms

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Efficient Approach for Repeated Patterns Mining Based on Indent Shape of HTML Documents

Efficient Approach for Repeated Patterns Mining Based on Ind...

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International Conference on Cyber-Enabled distributed Computing and Knowledge Discovery, CyberC

作者： Yanxu Zhu Gang Yin Huaimin Wang Dianxi Shi Xiang Rao Lin Yuan School of computer National Laboratory of Parallel and Distributed Processing National University of Defense Technology Changsha Hunan China College of Electronic Technology Information Engineering University Zhengzhou Henan China

Mining of repeated patterns from HTML documents is the key step towards Web-based data mining and knowledge extraction. Many web crawling applications need efficient repeated patterns mining techniques to generate their wrapper automatically. Existing approaches such as tree matching and string matching can detect repeated patterns with high precision, but their performance is still a challenge for practical web crawling applications. In this paper, we propose an efficient approach for mining repeated patterns based on indent shape of HTML document. Indent shape is a novel and simple model of HTML document, in which tandem repeated waves have strong association with the repeated patterns to be detected. By scanning an indent shape with a horizontal indent-line from bottom to top, the tandem repeated waves are identified by filtering the wave segments with low self-similarities. After that the boundary of HTML code corresponding to repeated patterns can be identified, which could be transformed to regular expressions formal-defined easily. Extensive experiments on two practical data sets retrieved from Internet show that our approach achieves high efficiency significantly, and its precision performance is also generally better than the existing approaches.

关键词： Shape HTML Data mining Web pages Vectors Visualization Algorithm design and analysis

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Scheduling in wireless ad hoc networks with successive interference cancellation

Scheduling in wireless ad hoc networks with successive inter...

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IEEE Annual Joint Conference: INFOCOM, IEEE Computer and Communications Societies

作者： Shaohe Lv Weihua Zhuang Xiaodong Wang Xingming Zhou National Laboratory of Parallel and Distributed Processing National University of Defense Technology Changsha Hunan China Department of Electrical and Computer Engineering University of Waterloo Waterloo ONT Canada

ISBN: (纸本)9781424499199

Successive interference cancellation (SIC) is an effective way of multipacket reception (MPR) to combat interference in wireless networks. To understand the potential MPR advantages, we study link scheduling in an ad hoc network with SIC at the physical layer. The fact that the links detected sequentially by SIC are correlated at the receiver poses key technical challenges. We characterize the link dependence and propose simultaneity graph (SG) to capture the effect of SIC. Then interference number is defined to measure the interference of a link. We show that scheduling over SG is NP-hard and the maximum interference number bounds the performance of maximal greedy schemes. An independent set based greedy scheme is explored to efficiently construct a maximal feasible schedule. Moreover, with careful selection of link ordering, we present a scheduling scheme that improves the bound. The performance is evaluated by both simulations and measurements in testbed. The throughput gain is on average 40% and up to 120% over IEEE 802.11. The complexity of SG is comparable with that of conflict graph, especially when the network size is not large.

关键词： Interference Silicon carbide Receivers Schedules Protocols Wireless networks Scheduling

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Managing Data-Objects in Dynamically Reconfigurable Caches

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Journal of Computer science & technology 2010年第2期25卷 232-245页

作者：杨学军吴俊杰曾坤唐玉华 National Laboratory for Parallel and Distributed Processing School of ComputerNational University of Defense Technology

The widening gap between processor and memory speeds makes cache an important issue in the computer system design. Compared with work set of programs, cache resource is often rare. Therefore, it is very important for a computer system to use cache efficiently. Toward a dynamically reconfigurable cache proposed recently, DOOC （Data- Object Oriented Cache）, this paper proposes a quantitative framework for analyzing the cache requirement of data-objects, which includes cache capacity, block size, associativity and coherence protocol. And a kind of graph coloring algorithm dealing with the competition between data-objects in the DOOC is proposed as well. Finally, we apply our approaches to the compiler management of DOOC. We test our approaches on both a single-core platform and a four-core platform. Compared with the traditional caches, the DOOC in both platforms achieves an average reduction of 44.98% and 49.69% in miss rate respectively. And its performance is very close to the ideal optimal cache.

关键词： cache data-object data reuse data-object oriented cache （DOOC） graph coloring

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Hierarchical diagnostic approach for performance problems in cloud computing platforms

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Tongxin Xuebao/Journal on Communications 2011年第7期32卷 114-124页

作者： Mi, Hai-Bo Wang, Huai-Min Cai, Hua Yin, Gang Zhou, Qi Sun, Ting-Tao Zhou, Yang-Fan National Laboratory for Parallel and Distributed Processing National University of Defense Technology Changsha 410073 China Computing Platform Alibaba Cloud Computing Company Hangzhou 310023 China Shenzhen Research Institute Chinese Univ. of Hong Kong Shenzhen 518057 China

A hierarchical diagnosis approach, namely Magnifier, was proposed, which models the execution path graph of a user request as component layer, module layer and function layer, and detects anomalies from higher layer to lower layer separately. Extensive experiments were conducted on the Alibaba cloud computing platform. The results indicate that, under the conditions of large volume of data and high complexity of execution paths, Magnifier can accurately and efficiently locate the prime causes of performance degradation.

关键词： Cloud computing

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