Micro-benchmarks for Cluster OpenMP Implementations: Memory Consistency Costs

The OpenMP memory model allows for a temporary view of shared memory that only needs to be made consistent when barrier or flush directives, including those that are implicit, are encountered. While this relaxed memory consistency model is key to developing cluster OpenMP implementations, it means that the memory performance of any given implementation is greatly affected by which memory is used, when it is used, and by which threads. In this work we propose a microbenchmark that can be used to measure memory consistency costs and present results for its application to two contrasting cluster OpenMP implementations, as well as comparing these results with data obtained from a hardware supported OpenMP environment.