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2014 IEEE 8th International Symposium on Service Oriented System Engineering

作者： Ziyang Li Zhaoning Zhang Huiba Li Yuxing Peng National Key Laboratory for Parallel and Distributed Processing National University of Defense Technology China

By analyzing the problems and challenges of virtual machine image store system in cloud computing environment, we present a cooperative persistent cache (CoCache) for virtual disks. CoCache takes advantage of the service ability of the cached nodes by providing virtual image data service for other nodes. CoCache can transfer data between nodes in a P2P pattern, for extending data service ability of the system. CoCache is realized in the kernel space of Linux, can support any kind of VMM. Experiments show that CoCache can effectively reduce the cost during virtual machines read data, and promote the service ability of virtual machine storage system. Layer-aware cache policy is proposed specially for improving cache hit rate in the multi-layer and multipath environment.

关键词： Virtual machining Servers Image storage Cloud computing Computer architecture System performance Cache storage

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Low-trimming-power design of on-chip optical networks

Low-trimming-power design of on-chip optical networks

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Photonic Networks and Devices, 2014

作者： Zhang, Luo Kefie, Wang Zhengbin, Pang Weixia, Xu School of Computer Science National University of Defense Technology Changsha 410073 China National Laboratory for Parallel and Distribution Processing National University of Defense Technology Changsha 410073 China

The trimming power of on-chip optical networks consisted by 105 microrings is simulated. The total trimming power is no larger than 14W from 20°C to 100°C, if the distribution of these rings is optimized. &#... 详细信息

ISBN: (纸本)9781557527370

关键词： Fiber optic networks

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3D Pipeline Contention: Asymmetric Full Duplex in Wireless Networks

3D Pipeline Contention: Asymmetric Full Duplex in Wireless N...

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IEEE International Conference on Computer Communications

作者： Shaohe Lv Xuan Dong Yong Lu Xiaoli Du Xiaodong Wang Yong Dou Xingming Zhou National Laboratory of Parallel and Distributed Processing National University of Defense Technology Changsha Hunan China

Coordination among users is an indispensable part in wireless networks for efficient medium access. Alone with the rapid increase of transmission rate, however, coordination time becomes insufferable. We present AFD, namely asymmetric full duplex, to achieve high coordination efficiency at nearly zero overhead. In AFD, channel contention is performed simultaneously with data transmission. We propose a 3D pipeline contention scheme where the contention process is divided into several parallel stages and executed in a pipelined manner in a 3D domain specified by time, frequency and spatial antenna. To mitigate the interference between the data packet and the contention signal, we adopt a singleton PN sequence as a contention pilot. AFD provides a novel network-scale full duplex capability. The performance is evaluated by both simulations and measurements in a testbed. AFD outperforms IEEE 802.11 significantly, i.e., the Jain's fairness index is around 0.95 with a throughput gain up to 120%.

关键词： Pipelines Data communication Antennas Three-dimensional displays Interference IEEE 802.11 Standards Time-frequency analysis

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A Discrete Data Dividing Approach for Erasure-Code-Based Storage Applications

A Discrete Data Dividing Approach for Erasure-Code-Based Sto...

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2014 IEEE 8th International Symposium on Service Oriented System Engineering

作者： Weidong Sun Yijie Wang Yongquan Fu Xiaoqiang Pei Science and Technology on Parallel and Distributed Processing Laboratory National University of Defense Technology Changsha Hunan P. R. China

Erasure codes are promising for improving the reliability of the storage system due to its space efficiency compared to the replication methods. Traditional erasure codes split data into equalsized data blocks and encode strips in different data blocks. This brings heavy repairing traffic when clients read parts of the data, since most strips read for repairing are not in the expected blocks. This paper proposes a novel discrete data dividing method to completely avoid this problem. The key idea is to encode strips from the same data block. We could see that for repairing failed blocks, the strips to be read are either in the same data block with corrupted strips or from the encoded strips. Therefore, no data is wasted. We design and implement this data layout into a HDFS-like storage system. Experiments over a small-scale testbed shows that the proposed discrete data divided method avoids downloading data blocks that are not needed for clients during the repairing operations.

关键词： Strips Decoding Encoding distributed databases Writing Reliability Magnetic heads

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Flexible Virtual Channel Power-Gating for High-Throughput and Low-Power Network-on-Chip

Flexible Virtual Channel Power-Gating for High-Throughput an...

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Euromicro Symposium on Digital System Design

作者： Feng Wang Xiantuo Tang Qinglin Wang Zuocheng Xing Hengzhu Liu Science and Technology on Parallel and Distributed Processing Laboratory National University of Defense Technology Changsha Hunan P. R. China

Power-gating is a representative circuit level technique to mitigate leakage power. While in low-power Network-on-Chip (NoC) design, the former fine-grained power-gating methods will decrease network performance due to serial wake-up latency and head-of-line blocking. Therefore, we propose a flexible Virtual Channel (VC) management scheme for fine-grained power-gating to achieve high throughput and low-power. The proposed power-gating method with the early wake-up is evaluated by using some synthetic workloads. When compared with an optimized early wake-up power-gating technique, it can improve performance effectively in medium and high network loads, and increases the network throughput by 15.7%~44.1% for different synthetic loads, while keeps network power consumption as low as the optimized method. For the PARSEC application traces of token based protocol, it can significantly decrease packet latency by 20.3% on average, however only increases less than 3.6% peak power when compared with the optimized method.

关键词： Throughput Radiation detectors Routing Process control Pipelines Power demand Ports (Computers)

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Signature-based fast access coordination in multicarrier wireless networks

Signature-based fast access coordination in multicarrier wir...

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General Assembly and Scientific Symposium, URSI

作者： Shaohe Lv Xuan Dong Hu Shen Xiaodong Wang Xingming Zhou National Laboratory of Parallel and Distributed Processing National University of Defense Technology Changsha Hunan China

Coordination among users is an indispensable part in wireless networks for efficient access control. Alone with the rapid increase of the data transmission rate, however, coordination time becomes insufferable, even several times higher than that for data transmission. We present SIF, a signature-based frequency-domain contention mechanism to achieve high coordination efficiency with low overhead. In SIF, different user is assigned by a different PN sequence as a signature. A contending user issues its signature on some specific OFDM subcarriers and uses the binary sequence of the ON/OFF states of all OFDM subcarriers to deliver the contend information. A signature-based detection method is proposed to detect the CVs of other nodes quickly and reliably. It is shown that, the collision probability of SIF is very low even in a large wireless networks, e.g., less than 0.2% with 100 users. Moreover, as SIF can complete the coordination within one slot in most cases, the throughput gain is up to 200% in comparison with 802.11.

关键词： IEEE 802.11 Standards Vectors Wireless networks OFDM Throughput Data communication Frequency-domain analysis

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IWFR: Exploiting full-duplex in wireless relay networks

IWFR: Exploiting full-duplex in wireless relay networks

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International Conference on Information science and technology (ICIST)

作者： Yong Lu Shaohe Lv Xiaodong Wang Xingming Zhou National Key Laboratory for Parallel and Distributed Processing School of Computer Science National University of Defense Technology Changsha Hunan China

Traditional wireless relay networks have large end-to-end time delay and low throughput because of the limit that it can't receive and forward at the same time. In this paper, we proposed IWFR: Immediate Wireless Full-Duplex Relay which exploits the advantages of full-duplex to shorten the end-to-end time delay and improve the throughput. At the same time, we designed a new implicit acknowledgement mechanism, which can eliminate the ACK overheads and evidently improve the throughput of the relay. To implement IWFR, we also modified the full-duplex node architecture to make it support for immediate relay. Simulation shows that IWFR shortens the end-to-end time delay by 60% on average and improves the throughput to 240% of the original relay.

关键词： Wireless communication Throughput Delay effects Wireless sensor networks Interference Relay networks (telecommunications)

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Accuracy evaluation of deep belief networks with fixed-point arithmetic

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Computer Modelling and New Technologies 2014年第6期18卷 7-14页

作者： Jiang, Jingfei Hu, Rongdong Mikel, Lujan Dou, Yong Science and Technology on Parallel and Distributed Processing Laboratory National University of Defense Technology ChangSha Hunan China University of Manchester Manchester United Kingdom

Deep Belief Networks (DBNs) are state-of-art Machine Learning techniques and one of the most important unsupervised learning algorithms. Training DBNs is computationally intensive which naturally leads to investigate FPGA acceleration. Fixed-point arithmetic can be used when implementing DBNs in FPGAs to reduce execution time, but it is not clear the implications for accuracy. Previous studies have focused only on accelerators using some fixed bit-widths. A contribution of this paper is to demonstrate the bit-width effect on various configurations of DBNs in a comprehensive way by experimental evaluation. Explicit performance changing points are found using various bit-widths. The impact of sigmoid function approximation, required part of DBNs, is evaluated. A solution of mixed bit-widths DBN is proposed, fitting the bit-widths of FPGA primitives and gaining similar performance to the software implementation. Our results provide a guide to inform the design choices on bit-widths when implementing DBNs in FPGAs documenting clearly the trade-off in accuracy.

关键词： Field programmable gate arrays (FPGA)

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Delayed Switch:Cloud Service Upgrade with Low Availability and Capacity Loss

Delayed Switch:Cloud Service Upgrade with Low Availability a...

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2014 IEEE 5th International Conference on Software Engineering and Service science

作者： Xue Ouyang Bo Ding Huaimin Wang Parallel and Distributed Laboratory School of Computer Science National University of Defense Technology

Cloud services must upgrade continuously in order to maintain ***,a large body of empirical evidence suggests that,upgrade procedures used in practice are failure-prone and often cause planned or unplanned *** this paper,we first define what is cloud service online upgrade,and then we analyze the shortcomings of current mainstream cloud service online upgrade *** particular,the mixed version problem along with rolling upgrade and the capacity loss problem brought by split mode upgrade have been *** that,we propose a solution called Delayed Switch,which can conduct cloud service upgrade with lower loss of availability and capacity in contrast with existing *** prove the performance of delayed switch in theory and develop a prototype system applying this *** by conducting experiments with a typical e-commerce service named Rubis,we validate the effectiveness and efficiency of our approach.

关键词： cloud service availability on-line upgrade mixed version problem split mode upgrade

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Synchronization Error Detection of MPI Programs by Symbolic Execution

Synchronization Error Detection of MPI Programs by Symbolic ...

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Asia-Pacific Conference on Software Engineering

作者： Xianjin Fu Zhenbang Chen Chun Huang Wei Dong Ji Wang College of Computer National University of Defense Technology Changsha China Science and Technology on Parallel and Distributed Processing Laboratory National University of Defense Technology Changsha China

ISBN: (纸本)9781479974276

Asynchrony based overlapping of computation and communication is commonly used in MPI applications. However, this overlapping introduces synchronization errors frequently in asynchronous MPI programming. In this paper, we propose a symbolic execution based method for detecting input-related synchronization errors. The path space of an MPI program is systematically explored, and the related operations of the synchronization errors in the program are checked specifically. In addition, two optimizations are proposed to improve the efficiency. We have implemented our method as a prototype tool based on the symbolic executor Cloud9. The results of the extensive experiments indicate the effectiveness of our method.

关键词： Synchronization Data communication Libraries Optimization Buffer storage Prototypes Schedules

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