Enabling Efficient Multithreaded MPI Communication through a Library-Based Implementation of MPI Endpoints

Abstract

Modern high-speed interconnection networks are designed with capabilities to support communication from multiple processor cores. The MPI endpoints extension has been proposed to ease process and thread count tradeoffs by enabling multithreaded MPI applications to efficiently drive independent network communication. In this work, we present the first implementation of the MPI endpoints interface and demonstrate the first applications running on this new interface. We use a novel library-based design that can be layered on top of any existing, production MPI implementation. Our approach uses proxy processes to isolate threads in an MPI job, eliminating threading overheads within the MPI library and allowing threads to achieve process-like communication performance. We evaluate the performance advantages of our implementation through several benchmarks and kernels. Performance results for the Lattice QCD Dslash kernel indicate that endpoints provides up to 2.9× improvement in communication performance and 1.87× overall performance improvement over a highly optimized hybrid MPI+OpenMP baseline on 128 processors.