Improving Read Performance with Online Access Pattern Analysis and Prefetching.

Among the major challenges of transitioning to exascale in HPC is the ubiquitous I/O bottleneck. For analysis and visualization applications in particular, this bottleneck is exacerbated by the write-once-read-many property of most scientific datasets combined with typically complex access patterns. One promising way to alleviate this problem is to recognize the application's access patterns and utilize them to prefetch data, thereby overlapping computation and I/O. However, current research methods for analyzing access patterns are either offline-only and/or lack the support for complex access patterns, such as high-dimensional strided or composition-based unstructured access patterns. Therefore, we propose an online analyzer capable of detecting both simple and complex access patterns with low computational and memory overhead and high accuracy. By combining our pattern detection with prefetching, we consistently observe run-time reductions, up to 26%, across 18 configurations of PIO-Bench and 4 configurations of a micro-benchmark with both structured and unstructured access patterns.