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예측 가능한 실행 시간을 가진 동적 메모리 할당 알고리즘
정성무,유해영,심재홍,김하진,최경희,정기현,Jeong, Seong-Mu,Yu, Hae-Yeong,Sim, Jae-Hong,Kim, Ha-Jin,Choe, Gyeong-Hui,Jeong, Gi-Hyeon 한국정보처리학회 2000 정보처리논문지 Vol.7 No.7
This paper proposes a dynamic storage allocation algorithm, QHF(quick-half-fit) for real-time systems. The proposed algorithm manages a free block list per each worked size for memory requests of small size, and a free block list per each power of 2 size for memory requests of large size. This algorithms uses the exact-fit policy for small sie requests and provides high memory utilization. The proposed algorithm also has the time complexity O(I) and enables us to easily estimate the worst case execution time (WCET). In order to confirm efficiency of the proposed algorithm, we compare he memory utilization of proposed algorithm with that of half-fit and binary buddy system that have also time complexity O(I). The simulation result shows that the proposed algorithm guarantees the constant WCET regardless of the system memory size and provides lower fragmentation ratio and allocation failure ratio thant other two algorithms.
TTT 타점법을 이용한 웹서버 파일 분포의 후미성 분석
정성무,이상용,장중순,송재신,유해영,최경희,Jung, Sung-Moo,Lee, Sang-Yong,Jang, Joong-Soon,Song, Jae-Shin,Yoo, Hae-Young,Choi, Kyung-Hee 한국정보처리학회 2003 정보처리학회논문지 A Vol.10 No.3
본 논문에서는 TTT 타점법을 이용하여 웹 서버가 서비스하는 파일의 크기에 대한 통계적 분포는 꼬리부분이 두꺼운 분포라는 것을 판단하는 방법을 제시한다. TTT 타점법은 신뢰성 공학에서 사용되는 방법으로써 TTT 통계량 타점결과의 직선성으로 지수분포 여부를 판단하는 방법이다. 본 연구에서 제안하는 방법을 모의실험과 실제 운영중인 웹서버의 자료를 사용하여 실험한 결과, 기존의 방법인 Hill 추정법과 LLCD 타점법에 비하여 후미성을 정확하게 판단하고 있으며, 판단의 효율성 면에서도 그들보다 우수하다는 것을 확인하였다. 특히 제안하는 방법은 기존의 방법이 웹서버의 파일 분포판정이나 통계학에서의 파레토 분포 판정시 나타날 수 있는 판정의 오류 가능성을 개선할 수 있다는 점도 확인하였다. In this paper, we propose a method of analysis to show the heavy-tailed statistical distribution of file sizes in web servers, using TTT plot technique. TTT plot technique, a well-known method in the area of reliability engineering, determines that a distribution of samples fellows a heavy tailed one when their TTT statistical plots are lied on a straight line. We performed an intensive simulation using data gathered from real web servers. The simulation indicates that the proposed method is superior to Hill estimation technique or LLCD plot method in efficiency of data analysis. Moreover, the proposed method eliminates the possible decision error, which Pareto distribution or traditional method might cause.
다양한 할당 정책을 지원하는 실시간 동적 메모리 할당 알고리즘
정성무 한국통신학회 2000 韓國通信學會論文誌 Vol.25 No.10
This paper proposes a real-time dynamic storage allocation algorithm QSHF(quick-segregated-half-fit) that provides various memory allocation policies. that manages a free block list per each word size for memory requests of small size good(segregated)-fit policy that manages a free list per proper range size for medium size requests and half-fit policy that manages a free list per proper range size for medium size requests and half-fit policy that manages a free list per each power of 2 size for large size requests. The proposed algorithm has the time complexit O(1) and makes us able to easily estimate the worst case execution time(WCET). This paper also suggests two algorithm that finds the proper free list for the requested memory size in predictable time and if the found list is empty then finds next available non-empty free list in fixed time. In order to confirm efficiency of the proposed algorithm we simulated the memory utilization of each memory allocation policy. The simulation result showed that each policy guarantees the constant WCET regardless of memory size but they have trade-off between memory utilization and list management overhead.