OpenSHMEM Non-blocking Data Movement Operations with MVAPICH2-X: Early Experiences.

PGAS models with a lightweight synchronization and shared memory abstraction, are seen as a good alternative to the Message Passing model for irregular communication patterns. OpenSHMEM is a library based PGAS model. OpenSHMEM 1.3 introduced Non-Blocking data movement operations to provide better asynchronous progress and overlap. In this paper, we present our experiences in designing Non-Blocking Put and Get operations on InfiniBand systems. Using the MVAPICH2-X runtime, we present the alternative designs for intra-node and inter-node operations. We also present a set of new benchmarks to analyze the latency, message rate performance, and communication/computation overlap benefits. The performance evaluation shows 7X improvement in the message rate. Furthermore, using a 3D-Stencil based application kernel, we assess the benefits of OpenSHMEM Non-Blocking extensions. We show 50% and 28% improvement on 27 and 64 processes, respectively.