A Low-Complexity Synchronization Based Cache Coherence Solution for Many Cores

  • Authors:
  • Wei Lin;DongRui Fan;He Huang;Nan Yuan;XiaoChun Ye

  • Affiliations:
  • -;-;-;-;-

  • Venue:
  • CIT '09 Proceedings of the 2009 Ninth IEEE International Conference on Computer and Information Technology - Volume 02
  • Year:
  • 2009

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Abstract

Computer architectures make a dramatic turn away from improving single-processor performance towards improved parallel performance through integrating many cores in one chip. However, providing directory based coherence protocols for these platforms is too complex and expensive. As a substitute, we propose a synchronization based cache coherence solution, which uses different cache policies according to three flexible software guided scopes (exclusion, producer and consumer scopes) to solve the data-race and coherence problem. Furthermore, this protocol implements word dirty bits (only one bit per word is needed in each L1 cache line) and a special hardware synchronization manager (HSM) to support multi-writer, the write-validate policy and to eliminate the remote un-cache spinning at the “flag”. We evaluate Godson-T, a platform supporting this protocol, against an idealized interleaved dual tag directory based protocol on the Splash2 and two bioinformatics benchmarks. The performance of the synch-based protocol is degraded only at 3.2% on average, but the real chip area is reduced at 32% even if the overhead of HSM is included.