Exploiting Offload Enabled Network Interfaces

Network interface cards are one of the key components to achieve efficient parallel performance. In the past, they have gained new functionalities such as lossless transmissionand remote direct memory access that are now ubiquitous in high-performance systems. Prototypes of next generation network cards now offer new features that facilitate device programming. In this work, various possible uses of network offload features are explored. We use the Portals 4 interface specification as an example to demonstrate various techniques such as fully asynchronous, multi-schedule asynchronous, and solo collective communications. MPI collectives are used as a proof of concept for how to leverage our proposed semantics. In a solo collective, one or more processes can participate in a collective communication without being aware of it. This semantic enables fully asynchronous algorithms. We discuss how the application of the solo collectives can improve the performance of iterative methods, such as multigrid solvers. The results obtained show how this work may be used to accelerate existing MPI applications, but they also display how these techniques could ease the programming of algorithms outside of the Bulk Synchronous Parallel (BSP) model.