• Journal of the Korea Society of Computer and Information
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• v.3 no.2
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• pp.169-175
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• 1998

There is a shared multibuffer method which can preventing HOL blocking in ATM switch. However, the system still has a problem that reduces the performance of the system because of the cell loss. Therefore, in this paper, preventing of cell loss in non-contentional shared multibuffer switch is suggested. To prevent cell loss, a structure is suggested that a cell can be loss in a certain slot time is stored in the dedicated temporary memory so the cell can be transferred in the next slot time. The simulation result of the structure, this suggested system superior performance than the exited system in cell loss rate and throughput.

• Journal of KIISE:Computing Practices and Letters
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• v.10 no.2
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• pp.134-145
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• 2004

With rapid growth in the amount of data transferred on the Internet, traditional storage systems have reached the limits of their capacity and performance. SAN (Storage Area Network), which connects hosts to disk with the Fibre Channel switches, provides one of the powerful solutions to scale the data storage and servers. In this environment, the maintenance of data consistency among hosts is an important issue because multiple hosts share the files on disks attached to the SAN. To preserve data consistency, each host can execute the disk I/O whenever disk read and write operations are requested. However, frequent disk I/O requests cause the deterioration of the overall performance of a SAN cluster. In this paper, we introduce a SANtopia global buffer manager to improve the performance of a SAN cluster reducing the number of disk I/Os. We describe the design and algorithms of the SANtopia global buffer manager, which provides a buffer cache sharing mechanism among the hosts in the SAN cluster. Micro-benchmark results to measure the performance of block I/O operations show that the global buffer manager achieves speed-up by the factor of 1.8-12.8 compared with the existing method using disk I/O operations. Also, File system micro-benchmark results show that SANtopia file system with the global buffer manager improves performance by the factor of 1.06 in case of directories and 1.14 in case of files compared with the file system without a global buffer manager.

• Proceedings of the Korean Information Science Society Conference
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• 2000.10a
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• pp.36-38
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• 2000

데이터베이스 공유 시스템(Database Sharing System: DSS)은 고성능 트랜잭션 처리를 위해 다수 개의 컴퓨터를 연동하는 방식으로, 각 노드들은 디스크 계층에서 데이터베이스를 공유한다. DSS에서 각 노드는 빈번한 디스크 액세스를 피하기 위해 최근에 액세스한 데이터 페이지와 인덱스 페이지들을 자신의 지역 메모리 버퍼에 캐싱한다. 이때 노드가 항상 최신의 페이지를 사용할 수 있기 위해서는 지역 버퍼에 캐싱된 페이지들의 일관성을 지원하여야 한다. 본 논문에서는 데이터 페이지에 비해 빈번히 엑세스되는 인덱스 페이지의 정확성을 보장할 수 있는 캐쉬 일관성 제어 기법을 제안한다.

• Journal of KIISE:Databases
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• v.35 no.6
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• pp.469-480
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• 2008

A shared disk (SD) cluster couples multiple nodes for high performance transaction processing, and all the coupled nodes share a common database at the disk level. To reduce the number of disk accesses, each node caches database pages in its memory buffer. Since a particular page may be cached simultaneously in different nodes, cache consistency should be maintained to ensure that nodes can always access the most recent version of database pages. Most cache consistency schemes proposed in the SD cluster adopted LRU as a buffer replacement algorithm. In this paper, we first present four buffer replacement algorithms that consider the characteristics of the SD cluster. Then we compare the performance of the buffer replacement algorithms. We perform the experiments on a variety of cluster configurations and database workloads. The experiment results show that the proposed algorithms achieve performance improvement up to 5 times of LRU algorithm.

• Journal of the Korea Society for Simulation
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• v.28 no.3
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• pp.65-74
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• 2019

For many years, it has been widely studied on fork-join production systems but there is not much literature focusing on the finite buffer(s) of either individuals or shared, and generally distributed processing times. Usually, it is difficult to handle finite buffer(s) through a standard queueing theoretical approach. In this study, by using the max-plus algebraic approach we studied buffer-shared fork-join production systems with general processing times. However, because it cannot provide proper computational ways for performance measures, we developed simulation models using @RISK software and the expressions derived from max-plus algebra. From the simulation experiments, we compared some properties on waiting time with respect to a buffer capacity under two blocking policies: BBS (Blocking Before Service) and BAS (Blocking After Service).

• Journal of the Institute of Convergence Signal Processing
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• v.7 no.3
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• pp.136-142
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• 2006

Existing buffer management schemes for shared-memory output queueing switches can be classified into two types: In the first type, some constant amount of memory space is guaranteed to each virtual queue using static queue thresholds. The static threshold method (ST) belongs to this type. On the other hand, the second type of approach tries to maximize the buffer utilization in 머 locating buffer memories. The complete sharing (CS) method is classified into this type. In the case of CS, it is very hard to protect regular traffic from mis-behaving traffic flows while in the case of ST the thresholds can not be adjusted according to varying traffic conditions. In this paper, we propose a new buffer management method called weighted dynamic thresholds (WDT) which can process packet flows based on loss priorities for quality-of-service (QoS) functionalities with fairly high memory utilization factors. We verified the performance of the proposed scheme through computer simulations.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.10
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• pp.24-33
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• 2001

Delay, delay variation and packet loss rate are principal QoS(Quality of Service) elements of packet communication. This paper proposes a new buffer allocation mechanism to improve the packet loss performance in such a situation that multiple logical buffers share a single physical memory buffer. In the proposed buffer allocation mechanism, the movement of dynamic threshold follows a curved track instead of a straight line which is used in the DT(dynamic threshold) mechanism. In order evaluate the effectiveness of the proposed mechanism, it is compared with the existing previously proposed mechanisms in several aspects including NC(no control), ST(Static Threshold) and DT mechanisms.

• The KIPS Transactions:PartA
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• v.9A no.2
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• pp.147-162
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• 2002

Multi-processor system with fast I/O devices improves processing performance and reduces the bottleneck by I/O concentration. In the system, the Performance influenced by shared memory used for exchanging data between processors varies with configuration and utilization. This paper suggests a prediction model for buffer and shared memory optimization under interrupt recognition method using mailbox. Ethernet (IEEE 802.3) packets are used as the input of system and the amount of utilized memory is measured for different network bandwidth and burstiness. Some empirical studies show that the amount of buffer and shared memory varies with packet concentration rate as well as I/O bandwidth. And the studies also show the correlation between two memories.

• Proceedings of the Korean Information Science Society Conference
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• 1999.10b
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• pp.221-223
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• 1999

소프트웨어로 MPEG-1 디코더의 구현이 가능하다. 소프트웨어 MPEG-1 디코더의 문제 중 하나는 MPEG-1 압축 알고리즘의 특징상 각각의 영상들이 서로 다른 압축율로 압축되기 때문에 재생시에 디코더에 걸리는 부하가 매우 불규칙적이라는 점이다. 이 문제는 MPEG-1 디코더를 보다 작은 실행 단위인 쓰래드로 나누어 처리함으로써 효율적으로 해결할 수 있다. 이때 독립적인 실행 흐름을 가지는 쓰래드들간의 데이터 전달을 위하여 공유버퍼를 사용하게 된다. 본 논문에서는 다중 쓰래드로 구성된 소프트웨어 MPEG-1 디코더에서 쓰래드들 간의 데이터 전달에 사용되는 공유 버퍼를 이용하여 오디오와 비디오 스트림의 동기화를 효과적으로 수행하는 기법을 소개한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1998.05a
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• pp.233-237
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• 1998

다중의 연속 미디어 데이타를 출력 마감시간(playout deadline)전에 검색 및 전송하여 자연스럽게 처리하기 위한 가장 효율적인 처리방안은 메모리 버퍼를 이용하는 것이다. 본 논문에서는 다중 스트림의 데이타 전송 요구 및 해제시의 버퍼 상태를 파악하여 버퍼를 동적으로 할당하고 물리작인 버퍼를 윈도우 크기의 논리버퍼로 분할하여 동적으로 관리하는 매핑관리자를 설계하여 버퍼이용률을 높일 수 있는 방안을 제시하였다. 또한, 서로 다른 소비율로 발생된 여분의 버퍼 공간을 활용할 수 있는 지능적인 선반입 기법과 마감시간을 고려한 전송 스케줄링 기법을 통해 실시간에 동기식으로 다중 미디어 스트림을 전송할 수 있는 동적 버퍼 관리 기법을 제안하였다. 마지막으로, 버퍼의 이용율을 높이기 위해 입출력 주기에 따라 버퍼 공간을 여러 스트림들이 파이프라이닝 방식으로 버퍼를 공유하는 기법과 잔여 버퍼공간의 할당 여부를 결정하기 위한 수락제어 기법을 적용하였다.