An efficient caching support for critical sections in large-scale shared-memory multiprocessors

Abstract

Directory-based and software-assisted schemes are the two main approaches to solving the cache coherence problem in large scale shared-memory multiprocessors. Until now, the emphasis in software-assisted schemes has been on ascertaining consistency within parallel constructs such as DoAll or DoAcross loops. In this paper, we propose a timestamped-based approach which also allows caching within critical sections. This scheme combines the best features of software-assisted and directory-based cache coherence protocols. It is based on a compile time analysis of interactions among critical sections and execution time local detection of cache incoherence by comparing the times when a variable was last written and last updated in the cache. A quantitative evaluation based on synthetic traces shows that this scheme results in hit ratios almost as high as in directory-based solutions while significantly reducing the network traffic.