• 한국컴퓨터정보학회논문지
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• 제11권6호
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• pp.125-131
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• 2006

기존의 디렉토리 일관성 기법에서는 독점 수정된 상태(exclusively-modified state) 데이터의 읽기 과정에서 흠 노드로의 데이터 갱신을 함께 수행한다. 그러나 이주 데이터(migratory data)는 한 프로세서에 의해 읽힌 뒤 곧이어 다른 프로세서에 의해 다시 변경되므로 흠 노드로의 데이터 갱신이 전혀 무의미하게 된다. 따라서 본 논문에서는 기존의 프로토콜을 개선하여 이와 같이 불필요한 흠 노드 갱신을 줄이는 개선된 방법을 제안하고 병렬 컴퓨터 시뮬레이터를 통해 프로토콜의 성능을 측정하였다. 실험을 통해 이주 데이터의 빈도가 높은 병렬 프로그램에서 제안된 기법이 캐쉬 일관성 트래픽과 네트워크 지연 시간이 크게 개선됨을 알 수 있었다.

• 대한전기학회논문지:시스템및제어부문D
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• 제54권10호
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• pp.615-619
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• 2005

Token coherence protocol has many good reasons against snooping/directory-based protocol in terms of latency, bandwidth, and complexity. Token counting easily maintains correctness of the protocol without global ordering of request which is basis of other dominant cache coherence protocols. But this lack of global ordering causes starvation which is not happening in snooping/directory-based protocols. Token coherence protocol solves this problem by providing an emergency mechanism called persistent request. It enforces other processors in the competition (or accessing same shared memory block, to give up their tokens to feed a starving processor. However, as the number of processors grows in a system, the frequency of starvation occurrence increases. In other words, the situation where persistent request occurs becomes too frequent to be emergent. As the frequency of persistent requests increases, not only the cost of each persistent matters since it is based on broadcasting to all processors, but also the increased traffic of persistent requests will saturate the bandwidth of multiprocessor interconnection network. This paper proposes a new request mechanism that defines order of requests to reduce occurrence of persistent requests. This ordering mechanism has been designed to be decentralized since centralized mechanism in both snooping-based protocol and directory-based protocol is one of primary reasons why token coherence protocol has advantage in terms of latency and bandwidth against these two dominant Protocols.