hwloc: A Generic Framework for Managing Hardware Affinities in HPC Applications

• Published in: 2010 18th Euromicro Conference on Parallel, Distributed and Network-based Processing pp. 180 - 186
• Main Authors: Broquedis, Franois, Clet-Ortega, Jerome, Moreaud, Stephanie, Furmento, Nathalie, Goglin, Brice, Mercier, Guillaume, Thibault, Samuel, Namyst, Raymond
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01-02-2010
• Subjects: Application software; Bandwidth; Computer architecture; Concurrent computing; Hardware Topology Affinities Placement MPI OpenMP; Memory management; Multicore processing; Software libraries
• DOI: 10.1109/PDP.2010.67
• EISSN: 2377-5750
• ISBN: 9781424456727; 142445672X
• ISSN: 1066-6192

The increasing numbers of cores, shared caches and memory nodes within machines introduces a complex hardware topology. High-performance computing applications now have to carefully adapt their placement and behavior according to the underlying hierarchy of hardware resources and their software affinities. We introduce the Hardware Locality (hwloc) software which gathers hardware information about processors, caches, memory nodes and more, and exposes it to applications and runtime systems in a abstracted and portable hierarchical manner. hwloc may significantly help performance by having runtime systems place their tasks or adapt their communication strategies depending on hardware affinities. We show that hwloc can already be used by popular high-performance OpenMP or MPI software. Indeed, scheduling OpenMP threads according to their affinities or placing MPI processes according to their communication patterns shows interesting performance improvement thanks to hwloc. An optimized MPI communication strategy may also be dynamically chosen according to the location of the communicating processes in the machine and its hardware characteristics.