An Implementation of OFI Libfabric in Support of Multithreaded PGAS Solutions

In this paper, we present an implementation of the OpenFabrics Interfaces (OFI) libfabric API in support of multithreaded PGAS programming models. Specifically, we describe a libfabric provider implementation for the Cray XCTM system using the Generic Network Interface (GNI) library. OFI libfabric is a new portable network API designed to address the needs of high performance networking software. In fact, the PGAS community was specifically targeted to provide input during the design phase, and the requirements of the community were directly addressed. The Cray XC is a system designed to meet the needs of multithreaded PGAS applications, and thus the implementation of libfabric for the GNI library provides a unique opportunity to evaluate a provider. We present initial results from our GNI provider that show good multithreaded performance and scaling for one-sided libfabric operations, which represent the bulk of data transfer operations in PGAS applications. We also show initial results for two-sided operations that are often needed for bootstrapping and barrier-style operations.