FALCON-X: Zero-copy MPI derived datatype processing on modern CPU and GPU architectures

This paper addresses the challenges of MPI derived datatype processing and proposes FALCON-X - A Fast and Low-overhead Communication framework for optimized zero-copy intra-node derived datatype communication on emerging CPU/GPU architectures. We quantify various performance bottlenecks such as memory layout translation and copy overheads for highly fragmented MPI datatypes and propose novel pipelining and memoization-based designs to achieve efficient derived datatype communication. In addition, we also propose enhancements to the MPI standard to address the semantic limitations. The experimental evaluations show that our proposed designs significantly improve the intra-node communication latency and bandwidth over state-of-the-art MPI libraries on modern CPU and GPU systems. By using representative application kernels such as MILC, WRF, NAS_MG, Specfem3D, and Stencils on three different CPU architectures and two different GPU systems including DGX-2, we demonstrate up to 5.5x improvement on multi-core CPUs and 120x benefits on DXG-2 GPU system over state-of-the-art designs in other MPI libraries. (C) 2020 Elsevier Inc. All rights reserved.