• Proceedings of the Korean Information Science Society Conference
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• 2001.04a
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• pp.352-354
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• 2001

효율적인 웹 캐쉬 교체 알고리즘을 통해 웹 서버와 네트워크의 부하를 감소시킬 수 있으며, 이에 따라 사용자가 요청한 문서에 대한 응답시간과 지연시간을 효과적으로 개선시킬 수 있다. 기존에 연구된 교체 알고리즘 중 LRU-SIZE와 LRU-MIN 기법은 일차적으로 캐슁된 문서의 크기에 따라 교체를 하고 크기가 똑같은 경우에 한해서 LRU를 적용하여 교체를 한다. 그러나 LRU-SIZE와 LRU-MIN에 의해서 캐슁된 문서를 교체를 하면 크기의 차이가 크지 않으면서 자주 요청되는 문서가 교체될 수 있다. 본 논문에서는 캐슁된 문서 크기의 로그화에 따라 구성된 그룹에서 자주 요청되지 않는 문서를 교체하는 알고리즘을 제안한다. 로그화를 통해 크기의 차이가 적은 문서들이 같은 그룹으로 설정되어 비교되기 때문에 자주 요청되는 문서들이 크기의 차이가 적은 문서에 의해 교체되는 것을 막을 수 있다. 성능 평가를 통해 제안한 교체 알고리즘이 다른 기법에 비해 높은 hit ratio를 나타냄을 보여준다.

• Proceedings of the Korean Information Science Society Conference
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• 2003.04a
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• pp.85-87
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• 2003

무선환경과 모바일 기기의 발달되고, 모바일 단말기의 보편화로 인해 유선환경에서 제공되던 각종 멀티미디어 서비스가 무선환경으로 옮겨가고 있다. 기존의 웹캐쉬 정책은 그 성능을 이미 검증 받았다. 그러나 그런 정책들은 인기도와 네트워크의 상태만을 고려했기 때문에 무선환경에서는 적합하지 않다. 본 논문에서는 무선환경에서 모바일 호스트의 이동성과 미디어 스트림의 특성을 고려한 캐쉬 교체 정책인 M-LRU를 제안한다. 그리고, 시뮬레이션을 통하여 기존의 LRU정책과 제안한 M-LRU 정책을 비교하였으며, 8-9%의 성능향상이 되었다는 것을 보여준다.

• Proceedings of the Korean Information Science Society Conference
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• 2002.10c
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• pp.409-411
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• 2002

본 논문에서는 스트리밍 미디어 캐슁 서버의 효율적인 캐슁 구조를 위하여 참조 횟수, 참조량, 참조 시간 둥의 정량적인 인자들과 사용자 요구 주기를 적용하여 최근 참조 경향에 높은 가중치를 부여함으로써 변화하는 콘텐츠 선호 경향에 빠르게 적응하는 가중치 기반의 캐쉬 교체 정책을 제안한다. 성능 분석은 시뮬레이션 환경 구축을 통해 실험하였으며 LRU, LFU와 SEG 캐쉬 정책과 비교 분석하여 향상된 결과를 보였다.

• Journal of KIISE:Computer Systems and Theory
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• v.31 no.11
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• pp.643-657
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• 2004

The chordal ring based CC-NUMA system contains many links to transmit transactions between a local node and a remote node because of its structural characteristics. However, the inclination that the transactions concentrate on the ring link increases both the traffic of the ring link and the response time, which degrades the overall performance of the chordal ring based CC-NUMA system. In this paper we suggest a new remote cache replacement policy that considers both the number of total links and the number of ring links to traverse for the transactions. Our proposed replacement policy can balance data between the ring link and the chordal link properly because it reflects the characteristics of chordal ring based CC-NUMA system well.

• Proceedings of the Korean Information Science Society Conference
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• 2000.10a
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• pp.305-307
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• 2000

이 논문은 OGC에서 제안하는 3계층 구조의 웹 매핑 테스트베드(Web Mapping Testbed) 환경에서 각 계층간의 통신량과 데이터 변화량으로 인한 속도 저하 문제를 해결하고자 한다. 이를 위해, 다수의 클라이언트가 일정 시간 내에 공통으로 접근하는 지도 영역에 대한 미들웨어 컴포넌트들의 중복된 작업 수를 줄이기 위해 맵 서버 컴포넌트들 간에 공유 캐쉬를 사용하는 구조를 설계 및 구현한다. 이 논문에서 제시하는 미들웨어의 캐쉬 구조는 전체 데이터 세트의 영역을 일정 간격의 그리드 셀로 나누어 관리함으로써 캐쉬 단위의 관리 비용을 줄이고 캐쉬를 효율적으로 사용한다. 또한, 기존의 교체 전략 기법을 접목하여, 다수의 클라이언트의 관심 대상인 영역을 중심으로 캐쉬를 유지하기 위해 접근 빈도수와 최근 사용 시간을 고려한 교체 전략을 사용한다.

• Journal of KIISE:Computer Systems and Theory
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• v.32 no.11_12
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• pp.663-674
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• 2005

We propose a system aimed at achieving high energy-delay efficiency by using adaptive victim caches. Particularly, we investigate methods to improve the hit rates in the first level of memory hierarchy, which reduces the number of accesses to mort power consuming memory structures such as L2 cache. Victim cache is a memory element for reducing conflict misses in a direct-mapped L1 cache. We present two techniques to fill the victim cache with the blocks that have higher probability to be re-reqeusted by processor. Hit-based victim cache ks tilled with the blocks which were referenced frequently by processor. Replacement-based victim cache is filled with the blocks which were evicted from the sets where block replacements had happened frequently According to our simulations, replacement-based victim cache scheme outperforms the conventional victim cache scheme about $2\%$ on average and refutes the power consumption by up to $8\%$.

• Journal of KIISE:Computer Systems and Theory
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• v.31 no.12
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• pp.704-715
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• 2004

Recently, a single or multi processor system uses the hierarchical memory structure to reduce the time gap between processor clock rate and memory access time. A cache memory system includes especially two or three levels of caches to reduce this time gap. Moreover, one of the most important things In the hierarchical memory system is the hit rate in level 1 cache, because level 1 cache interfaces directly with the processor. Therefore, the high hit rate in level 1 cache is critical for system performance. A victim cache, another high level cache, is also important to assist level 1 cache by reducing the conflict miss in high level cache. In this paper, we propose the advanced high level cache management scheme based on the processor reuse information. This technique is a kind of cache replacement policy which uses the frequency of processor's memory accesses and makes the higher frequency address of the cache location reside longer in cache than the lower one. With this scheme, we simulate our policy using Augmint, the event-driven simulator, and analyze the simulation results. The simulation results show that the modified processor reuse information scheme(LIVMR) outperforms the level 1 with the simple victim cache(LIV), 6.7% in maximum and 0.5% in average, and performance benefits become larger as the number of processors increases.

• Proceedings of the Korea Contents Association Conference
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• 2003.11a
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• pp.234-244
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• 2003

In distributed file-systems, cooperative caching algorithm which owns the data cached at each node jointly is used to reduce an expense of disk access. Cooperative caching algorithm is the method that increases a cache hit-ratio and decrease a disk access as it holds the cache information of distributed systems in common and makes cache larger virtually. Recently, several cooperative caching algorithms decrease the message costs by using approximate information of the cache and increase the cache hit-ratio by using local and global cache fields dynamically. And they have an advantage that increases the whole field hit-ratio by sending a replaced block to the idel node on cache replacement in order to maintain the replaced block in the cache field. However the wrong approximate information deteriorates the performance, the concistency maintenance goes to great expense to exchange messeges and the cost that manages Age-information of each node to choose the idle node increases. In this thesis, we propose a cooperative cache algorithm that maintains correct cache information, minimizes the maintance cost for consistency and the management cost for cache Age-information. Also, we show the superiority of our algorithm through the performance evaluation.

• The Journal of the Korea Contents Association
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• v.8 no.11
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• pp.57-64
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• 2008

The data grid computing provides geographically distributed storage resources to solve computational problems with large-scale data. Unlike cache replacement policies in virtual memory or web-caching replacement, an optimal file replacement policy for data grids is the one of the important problems by the fact that file size is very large. The traditional file replacement policies such as LRU(Least Recently Used), LCB-K(Least Cost Beneficial based on K), EBR(Economic-based cache replacement), LVCT(Least Value-based on Caching Time) have the problem that they have to predict requests or need additional resources to file replacement. To solve theses problems, this paper propose SBR-k(Sized-based replacement-k) that replaces files based on file size. The proposed policy considers file size to reduce the number of files corresponding to a requested file rather than forecasting the uncertain future for replacement. The results of the simulation show that hit ratio was similar when the cache size was small, but the proposed policy was superior to traditional policies when the cache size was large.

• Journal of KIISE:Computer Systems and Theory
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• v.27 no.6
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• pp.583-591
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• 2000

Caching mechanisms have been studied extensively to buffer the speed gap of hierarchical storages in the context of cache memory, paging system, and buffer management system. As the wide-area distributed environments such as the WWW extend broadly, caching of remote objects becomes more and more important. In the wide-area distributed environments, the cost and the benefit of caching an object is not uniform due to the location of the object; which should be considered in the cache replacement algorithms. For online operation, the time complexity of the replacement algorithm should not be excessive. To date, most replacement algorithms for the wide-area distributed environments do not meet both the non-uniformity of objects and the time complexity constraint. This paper proposes a replacement algorithm which considers the non-uniformity of objects properly; it also allows for an efficient implementation. Trace-driven simulations show that proposed algorithm outperforms existing replacement algorithms.