Revisiting rendezvous protocols in the context of RDMA-capable host channel adapters and many-core processors
Masamichi Takagi, Yuichi Nakamura, Atsushi Hori, Balazs Gerofi, Yutaka Ishikawa · 2013
We revisit RDMA-based rendezvous protocols in MPI in the context of cluster computer with RDMA-capable HCA and many-core processors, and propose two improved protocols. The conventional sender-initiate rendezvous protocols cause costly processor-device communications via PCI bus on detecting completion of RDMA transfer. The conventional receiver-initiate rendezvous protocols need to send extra control messages when a value of the memory-slot to poll in the receive buffer has the same value as the send buffer. The first proposed protocol implements polling on a memory-slot in the receive buffer to eliminate the processor-device communications. The second proposed protocol randomizes the value of the memory-slot to poll to reduce extra control messages. We have evaluated the proposed protocols using micro-benchmarks and NAS Parallel Benchmarks. One of the proposed protocols has a benefit compared to the conventional protocols. And the second proposed protocol reduces the execution time by up to 11.14% compared to the first protocol.