A Scalable Cache Coherent Scheme Exploiting Wormhole Routing Networks

  • Authors:
  • Yunseok Rhee;Joonwon Lee

  • Affiliations:
  • -;-

  • Venue:
  • HPCA '99 Proceedings of the 5th International Symposium on High Performance Computer Architecture
  • Year:
  • 1999

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Abstract

Large scale shared memory multiprocessors favor a directory-based cache coherence scheme for its scalability. The directory space needed to record the information for sharers has a complexity of O(N^2) when a full-mapped vector is used for an N-node system. Though this overhead can be reduced by limiting the directory size assuming that the sharing degree is small, it will experience significant inefficiency when a data is widely shared.In this paper, we propose a new directory scheme and a cache coherence scheme based on it for a mesh interconnection. Deterministic and wormhole routing enables a pointer to represent a set of nodes. Also a message traversing on the mesh performs a broadcast mission to a set of nodes without extra traffic, which can be utilized for the cache coherence problem. Only a slight change on a generic router is needed to implement our scheme. This scheme is also applicable to any k-ary n-cube networks including a mesh.