Scalable NIC Architecture to Support Offloading of Large Scale MPI Barrier

MPI collective communication overhead dominates the communication cost for large scale parallel computers, scalability and operation latency for collective communication is critical for next generation computers. This paper proposes a fast and scalable barrier communication offload approach which supports millions of compute cores. Following our approach, the barrier operation sequence is packed by host MPI driver into the barrier "descriptor", which is pushed to the NIC Network-Interfaces. The NIC can complete the barrier automatically following its algorithm descriptor. Our approach leverages an enhanced dissemination algorithm which is suitable for current large scale networks. We show that our approach achieves both barrier performance and scalability, especially for large scale computer system. This paper also proposes an extendable and easy-to-implement NIC architecture supporting barrier offload communication and also other communication pattern.