Mechanisms for cooperative shared memory

This paper explores the complexity of implementing directory protocols by examining their mechanisms - primitive operations on directories, caches, and network interfaces. We compare the following protocols: Dir<inf>1</inf>B, Dir<inf>4</inf>B, Dir<inf>4</inf>NB, Dir<inf>n</inf>NB, Dir<inf>1</inf>SW and an improved version of Dir<inf>1</inf>SW (Dir<inf>1</inf>SW<sup>+</sup>). The comparison shows that the mechanisms and mechanism sequencing of Dir<inf>1</inf>SW and Dir<inf>1</inf>SW<sup>+</sup> are simpler than those for other protocols. We also compare protocol performance by running eight benchmarks on 32 processor systems. Simulations show that Dir<inf>1</inf>SW<sup>+</sup>'s performance is comparable to more complex directory protocols. The significant disparity in hardware complexity and the small difference in performance argue that Dir<inf>1</inf>SW<sup>+</sup> may be a more effective use of resources. The small performance difference is attributable to two factors: the low degree of sharing in the benchmarks and Check-In/Check-Out (CICO) directives.

Published in:
Proceedings of the International Symposium on Computer Architecture, 156 - 167
Presented at:
20th International Symposium on Computer Architecture, San Diego, CA, May

 Record created 2009-04-06, last modified 2018-03-18

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