Latest Articles from JUCS - Journal of Universal Computer Science Latest 7 Articles from JUCS - Journal of Universal Computer Science https://lib.jucs.org/ Fri, 29 Mar 2024 03:30:49 +0200 Pensoft FeedCreator https://lib.jucs.org/i/logo.jpg Latest Articles from JUCS - Journal of Universal Computer Science https://lib.jucs.org/ Scalable Distributed Metadata Server Based on Nonblocking Transactions https://lib.jucs.org/article/23991/ JUCS - Journal of Universal Computer Science 26(1): 89-106

DOI: 10.3897/jucs.2020.006

Authors: Kohei Hiraga, Osamu Tatebe, Hideyuki Kawashima

Abstract: Metadata performance scalability is critically important in high-performance computing when accessing many small files from millions of clients. This paper proposes a design of a scalable distributed metadata server, PPMDS, for parallel file systems using multiple key-value servers. In PPMDS, hierarchical namespace of a file system is efficiently managed by multiple servers. Multiple entries can be atomically updated using a nonblocking distributed transaction based on an algorithm of dynamic software transactional memory. This paper also proposes optimizations to further improve the metadata performance by introducing a server-side transaction processing, multiple readers, and a shared lock mode, which reduce the number of remote procedure calls and prevent unnecessary blocking. Performance evaluation shows the scalable performance up to 3 servers, and achieves 62,000 operations per second, which is 2.58x performance improvement compared to a single metadata performance.

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Research Article Tue, 28 Jan 2020 00:00:00 +0200
Precise Performance Characterization of Antivirus on the File System Operations https://lib.jucs.org/article/22647/ JUCS - Journal of Universal Computer Science 25(9): 1089-1108

DOI: 10.3217/jucs-025-09-1089

Authors: Mohammed Al-Saleh, Hanan Hamdan

Abstract: The Antivirus (AV) is of an important concern to the end-users community. Mainly, the AV achieves security by scanning data against its database of virus signatures. In addition, the AV tries to reach a pleasant balance between security and United States of Americability. When to scan data is an important design decision an AV has to make. Because AVs are equipped with on-access scanners that scan files when necessary, we want to have a fine-grained approach that provides us with high precision explanation of the performance impact of the AVs on different file system operations. Microsofts minifilter driver technology helps us achieve exactly what we want. By deploying a minifilter driver, we show that most overhead of the tested AVs are greatly imposed on the OPEN operation. Interestingly, we also show that the AV greatly enhances the timing for the READ operation. Finally, the WRITE and CLEANUP operations show almost no differences in terms of performance.

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Research Article Sat, 28 Sep 2019 00:00:00 +0300
Scheduling Mandatory-Optional Real-Time Tasks in Homogeneous Multi-Core Systems with Energy Constraints Using Bio-Inspired Meta-Heuristics https://lib.jucs.org/article/22604/ JUCS - Journal of Universal Computer Science 25(4): 390-417

DOI: 10.3217/jucs-025-04-0390

Authors: Matias Micheletto, Rodrigo Santos, Javier Orozco

Abstract: In this paper we present meta-heuristics to solve the energy aware reward based scheduling of real-time tasks with mandatory and optional parts in homogeneous multi-core processors. The problem is NP-Hard. An objective function to maximize the performance of the system considering the execution of optional parts, the benefits of slowing down the processor and a penalty for changing the operation power-mode is introduced together with a set of constraints that guarantee the real-time performance of the system. The meta-heuristics are the bio-inspired methods Particle Swarm Optimization and Genetic Algorithm. Experiments are made to evaluate the proposed algorithms using a set of synthetic systems of tasks. As these have been used previously with an Integer Lineal Programming approach, the results are compared and show that the solutions obtained with bio-inspired methods are within the Pareto frontier and obtained in less time. Finally, precedence related tasks systems are analyzed and the meta-heuristics proposed are extended to solve also this kind of systems. The evaluation is made by solving a traditional example of the real-time precedence related tasks systems on multiprocessors. The solutions obtained through the methods proposed in this paper are good and show that the methods are competitive. In all cases, the solutions are similar to the ones provided by other methods but obtained in less time and with fewer iterations.

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Research Article Sun, 28 Apr 2019 00:00:00 +0300
Performance Evaluation of Recent Windows Operating Systems https://lib.jucs.org/article/22929/ JUCS - Journal of Universal Computer Science 18(2): 218-263

DOI: 10.3217/jucs-018-02-0218

Authors: Goran Martinovic, Josip Balen, Bojan Cukic

Abstract: The primary goal of most OSs (Operating Systems) is the efficient use of computer systems software and hardware resources. Since Windows OSs are most widely used OS for personal computers, they need to satisfy needs of all different kind of computer systems users. In comparison with Windows XP, new versions of the Windows OS; namely Windows Vista and Windows 7, introduce a number of new features and enhancements. Furthermore, performance improvement was imposed as one of the key design goals for both Windows Vista and Windows 7. This paper presents a performance evaluation of three latest versions of the Microsoft OS for personal computers; namely Windows XP, Windows Vista and Windows 7. OS performance measurement is done by means of a set of benchmark applications in the controlled environment. To ensure accurate, reliable and repeatable performance measurement results, we have created a performance measurement process and a performance evaluation model. Special emphasis is placed on evaluation areas with the greatest impact on the performance: CPU cheduling, memory management, graphic subsystem management, hard disk drive management and network performance. To determine the Windows OSs performance in different environments, performance measurement is done in three experiments. Experimental results indicate that Windows Vista and Windows 7 have several performance improvements on the stand-alone high-end computer system, but Windows XP outperforms Windows Vista and Windows 7 on the stand-alone low-end computer system. Furthermore, on network computer system Windows Vista and Windows 7 show network performance improvements mostly for the traffic with medium-sized packets.

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Research Article Sat, 28 Jan 2012 00:00:00 +0200
Performance Evaluation of Snort under Windows 7 and Windows Server 2008 https://lib.jucs.org/article/30010/ JUCS - Journal of Universal Computer Science 17(11): 1605-1622

DOI: 10.3217/jucs-017-11-1605

Authors: Khaled Salah, Mojeeb-Al-Rhman Al-Khiaty, Rashad Ahmed, Adnan Mahdi

Abstract: Snort is the most widely deployed network intrusion detection system (NIDS) worldwide, with millions of downloads to date. PC-based Snort typically runs on either Linux or Windows operating systems. In this paper, we present an experimental evaluation and comparison of the performance of Snort NIDS when running under the two newly released operating systems of Windows 7 and Windows Server 2008. Snort's performance is measured when subjecting a PC host running Snort to both normal and malicious traffic. Snort's performance is evaluated and compared in terms of throughput and packet loss. In order to offer sound interpretations and get a better insight into the behaviour of Snort, we also measure the packet loss encountered at the kernel level. In addition, we study the impact of running Snort under different system configurations which include CPU scheduling priority given to user applications or kernel services, uni and multiprocessor environment, and processor affinity.

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Research Article Fri, 1 Jul 2011 00:00:00 +0300
The Use of Runtime Reconfiguration on FPGA Circuits to Increase the Performance of the AES Algorithm Implementation https://lib.jucs.org/article/28747/ JUCS - Journal of Universal Computer Science 13(3): 349-362

DOI: 10.3217/jucs-013-03-0349

Authors: Oscar PĂ©rez, Yves Berviller, Camel Tanougast, Serge Weber

Abstract: This article presents an architecture that encrypts data with the AES algorithm. This architecture can be implemented on the Xilinx Virtex II FPGA family, by applying pipelining and dynamic total reconfiguration (DTR). The originality of our implementation is that it computes sequentially in the FPGA the Key and Cipher part of the AES algorithm. This dynamic reconfiguration implementation allows a good optimization of logic resources with a high throughput. This architecture employs only 11619 slices allowing a considerable economy of the resources and reaching a maximum throughput of 44 Gbps.

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Research Article Wed, 28 Mar 2007 00:00:00 +0300
Performance of Switch Blocking on Multithreaded Architectures https://lib.jucs.org/article/27719/ JUCS - Journal of Universal Computer Science 6(10): 928-947

DOI: 10.3217/jucs-006-10-0928

Authors: K. Gopinath, M. K. Narasinhan

Abstract: Block multithreaded architectures tolerate large memory and synchronization latencies by switching contexts on every remote-memory-access or on a failed synchronization request. We study the performance of a waiting mechanism called switch-blocking where waiting threads are disabled (but not unloaded) and signalled at the completion of the wait in comparison with switch_spinning where waiting threads poll and execute in a round-robin fashion. We present an implementation of switch-blocking on a cycle-by-cycle simulator for Alewife (a block multithreaded machine) for both remote memory accesses and synchronization operations and discuss results from the simulator. Our results indicate that while switch-blocking almost always has better performance than switch-spinning, its performance is similar to switch-spinning under heavy lock contention. Support for switch-blocking for remote memory accesses may be appropriate in the future due to their strong interactions with synchronization operations.

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Research Article Sat, 28 Oct 2000 00:00:00 +0300