Journal of KIISE:Databases (한국정보과학회논문지:데이타베이스)

Korean Institute of Information Scientists and Engineers (한국정보과학회)
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Effective Reference Probability Incorporating the Effect of Expiration Time in Web Cache

웹 캐쉬에서 만기시간의 영향을 고려한 유효참조확률

  • Lee, Jeong-Joon (Dept. of Computer Science, Korea Advanced Institute of Science and Technology) ;
  • Moon, Yang-Se (Dept. of Computer Science, Korea Advanced Institute of Science and Technology) ;
  • Whang, Kyu-Young (Dept. of Computer Science, Korea Advanced Institute of Science and Technology) ;
  • Hong, Eui-Kyung
  • 이정준 (한국과학기술원 전산학과) ;
  • 문양세 (한국과학기술원 전산학과) ;
  • 황규영 (한국과학기술원 전산학과) ;
  • 홍의경 (서울시립대학교 전산통계학과)
  • Published : 2001.12.01
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Abstract

Web caching has become an important problem addressing the performance issues in web applications. In this paper we propose a method that enhances the performance of web caching by incorporating the expiration time of web data we introduce the notion of the effective reference probability that incorporates the effect of expiration time into the reference probability used in the existing cache replacement algorithms .We formally define the effective reference probability and derive it theoretically using a probabilistic model. By simply replacing probabilities with the effective reference probability in the existing cache replacement algorithms we can take the effect of expiration time into account The results of performance evaluation through experiments show that the replacement algorithms using the effective reference probability always outperform the existing ones. The reason is that the proposed method precisely reflects the theoretical probability of getting the cache effect, and thus, incorporates the influence of the expiration time more effectively. In particular when the cache fraction is 0.05 and data update is comparatively frequent (i.e. the update frequency is more than 1/0 of the reference frequency) the performance enhancement is more than 30% in LRU-2 and 13% in Aggarwal's method (PSS integrating a refresh overhead factor) The results show that effective reference probability contributes significantly to the performance enhancement of the web cache in the presence of expiration time.

웹 캐쉬는 웹 응용의 성능향상을 위한 중요한 문제가 되었다. 본 논문에서는 웹 데이타에 부여 되는 만기시간(expiration time을 활용하여 웹 캐쉬의 성능을 향상시키는 방법을 제안한다. 먼저, 기존 캐 쉬 교체 알고리즘에서 사용된 참조확률에 만기시간의 영향을 반영한 유효참조확률(effective referenceprobability)의 개념을 제시한다. 그리고, 유효참조확률을 정형적으로 정의한 후, 확률적 모델 하에서 이 론적으로 유도한다. 기존의 교체 알고리즘에서 참조확률을 유효탐조확률로 대체하면 기존 교체 알고리즘에만기시간의 영향을 반영할 수 있다. 성능평가 결과, 유효참조확률을 사용한 알고리즘이 그렇지 않은 알고 리즘보다 항상 우수한 결과를 보였다. 이것은 제안한 방법이 만기시간을 고려하여 캐쉬효과를 얻을 이론적 인 확률을 정확히 반영한 방법으로서, 만기시간의 영향을 보다 효과적으로 반영하기 때문이다. 특히, 유효 참조확률은 캐쉬비율이 0.05이고 갱신이 비교적 자주 일어날 경우(갱신횟구가 참조횟수의 1/10이상인 경우)에 LRU-2의 경우 30% 이상. Aggarwal의 방법(refresh overhead factor가 통합된 PSS)의 경우 13%이상 성능을 개선하였다. 이 같은 결과는 유효참조확률이 만기시간이 주어지는 웹 캐쉬에서 크게 성능을 개선할 수 있음을 보여주고 있다.

Keywords

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