Experimental analysis of coherency behavior of shared memory scientific applications

We address the characterization of coherency traffic in shared memory scientific applications. In particular, we are focusing on intrinsic (i.e. architecture independent) coherency properties of scientific codes. The major goal of this study is to understand coherency behavior in particular to determine correlations between the activities of the key components: processors, cache lines, loops and so on. Based on a systematic experimentation study on the well known Splash 2 benchmarks, we discovered a few key properties of coherency behavior: unbalanced spread of coherency events over memory space, spatial properties of coherency events, concentration of coherency events on a very few loops, etc. Characterizing properly these properties is essential for both restructuring applications to improve coherency behavior and/or design new cost effective coherency mechanisms. Consequently, as a result of our characterization we suggest various research directions for improving performance of coherency actions.