An evaluative study on the effect of contention on message latencies in large supercomputers

Abhinav Bhatelé, Laxmikant V. Kalé

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Significant theoretical research was done on interconnect topologies and topology aware mapping for parallel computers in the 80s. With the deployment of virtual cutthrough, wormhole routing and faster interconnects, message latencies reduced and research in the area died down. This paper presents a study showing that with the emergence of very large supercomputers, typically connected as a 3D torus or mesh, topology effects have become important again. It presents an evaluative study on the effect of contention on message latencies on torus and mesh networks. The paper uses three MPI benchmarks to evaluate the effect of hops (links) traversed by messages, on their latencies. The benchmarks demonstrate that when multiple messages compete for network resources, link occupancy or contention can increase message latencies by up to a factor of 8 times. In other words, contention leads to increased message latencies and reduces effective available bandwidth for each message. This suggests that application developers should consider interconnect topologies when mapping tasks to processors in order to obtain the best performance. Results are shown for two parallel machines - ANL's Blue Gene/P and PSC's XT3.

Original languageEnglish (US)
Title of host publicationIPDPS 2009 - Proceedings of the 2009 IEEE International Parallel and Distributed Processing Symposium
DOIs
StatePublished - Nov 25 2009
Event23rd IEEE International Parallel and Distributed Processing Symposium, IPDPS 2009 - Rome, Italy
Duration: May 23 2009May 29 2009

Publication series

NameIPDPS 2009 - Proceedings of the 2009 IEEE International Parallel and Distributed Processing Symposium

Other

Other23rd IEEE International Parallel and Distributed Processing Symposium, IPDPS 2009
CountryItaly
CityRome
Period5/23/095/29/09

ASJC Scopus subject areas

  • Computational Theory and Mathematics
  • Hardware and Architecture
  • Software

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    Bhatelé, A., & Kalé, L. V. (2009). An evaluative study on the effect of contention on message latencies in large supercomputers. In IPDPS 2009 - Proceedings of the 2009 IEEE International Parallel and Distributed Processing Symposium [5161094] (IPDPS 2009 - Proceedings of the 2009 IEEE International Parallel and Distributed Processing Symposium). https://doi.org/10.1109/IPDPS.2009.5161094