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A Speculative and Adaptive MPI Rendezvous Protocol over RDMA-enabled Interconnects

Summary: 1
A Speculative and Adaptive MPI Rendezvous Protocol over RDMA-enabled
Mohammad J. Rashti Ahmad Afsahi1
Department of Electrical and Computer Engineering
Queen's University, Kingston, ON, CANADA K7L 3N6
mohammad.rashti@ece.queensu.ca ahmad.afsahi@queensu.ca
Overlapping computation with communication is a key technique to conceal the effect of
communication latency on the performance of parallel applications. MPI is a widely used message
passing standard for high performance computing. One of the most important factors in achieving a
good level of overlap is the MPI ability to make progress on outstanding communication operations. In
this paper, we propose a novel speculative MPI Rendezvous protocol that uses RDMA Read and RDMA
Write to effectively improve communication progress and consequently the overlap ability. Performance
results based on a modified MPICH2 implementation over 10-Gigabit iWARP Ethernet reveal a
significant (80-100%) improvement in receiver side overlap and progress ability. We have also observed
up to 30% improvement in application wait time for some NPB applications as well as the RADIX
application. For applications that do not benefit from this protocol, an adaptation mechanism is used to
stop the speculation to effectively reduce the protocol overhead.
Keyword: MPI Rendezvous Protocol, Overlap, Communication Progress, RDMA, High-Performance


Source: Afsahi, Ahmad - Department of Electrical and Computer Engineering, Queen's University (Kingston)


Collections: Computer Technologies and Information Sciences