Network Partitioning and Avoidable Contention

Yishai Oltchik, Oded Schwartz

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

1 Scopus citations

Abstract

Network contention frequently dominates the run time of parallel algorithms and limits scaling performance. Most previous studies mitigate or eliminate contention by utilizing one of several approaches: communication-minimizing algorithms; hotspot-avoiding routing schemes; topology-aware task mapping; or improving global network properties, such as bisection bandwidth, edge-expansion, partitioning, and network diameter. In practice, parallel jobs often use only a fraction of a host system. How do processor allocation policies affect contention within a partition? We utilize edge-isoperimetric analysis of network graphs to determine whether a network partition defined by a processor allocation has optimal internal bisection. Increasing the bisection allows a more efficient use of the network resources, decreasing or completely eliminating the link contention. We study torus networks and characterize partition geometries that maximize internal bisection bandwidth, and examine the allocation policies of Mira and JUQUEEN, the two largest publicly-accessible Blue∼Gene/Q torus-based supercomputers. Our analysis shows that the bisection bandwidth of their partitions can often be improved by changing the partitions' geometries, yielding up to a x2∼speedup for contention-bound workloads. Benchmark experiments validate the predictions. Our analysis applies to allocation policies of other networks.

Original languageAmerican English
Title of host publicationSPAA 2020 - Proceedings of the 32nd ACM Symposium on Parallelism in Algorithms and Architectures
PublisherAssociation for Computing Machinery
Pages563-565
Number of pages3
ISBN (Electronic)9781450369350
DOIs
StatePublished - 6 Jul 2020
Event32nd ACM Symposium on Parallelism in Algorithms and Architectures, SPAA 2020 - Virtual, Online, United States
Duration: 15 Jul 202017 Jul 2020

Publication series

NameAnnual ACM Symposium on Parallelism in Algorithms and Architectures

Conference

Conference32nd ACM Symposium on Parallelism in Algorithms and Architectures, SPAA 2020
Country/TerritoryUnited States
CityVirtual, Online
Period15/07/2017/07/20

Bibliographical note

Publisher Copyright:
© 2020 Owner/Author.

Keywords

  • contention-minimization
  • high-performance computing
  • network topologies
  • parallel computing
  • torus networks

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