On reducing false sharing while improving locality on shared memory multiprocessors

Mahmut Kandemir, Alok Choudhary, J. Ramanujam, Prith Banerjee

Research output: Contribution to journalConference articlepeer-review

6 Scopus citations


The performance of applications on large shared-memory multiprocessors with coherent caches depends on the interaction between the granularity of data sharing, the size of the coherence unit and the spatial locality exhibited by the applications, in addition to the amount of parallelism in the applications. Large coherence units are helpful in exploiting spatial locality, but worsen the effects of false sharing. We present a mathematical framework that allows a clean description of the relationship between spatial locality and false sharing. We first show how to identify a severe form of multiple-writer false sharing and then demonstrate the importance of the interaction between optimization techniques aimed at enhancing locality and the techniques oriented toward reducing false sharing. Given the conflicting requirements, a compiler based approach to this problem holds promise. We investigate the use of data transformations in addressing spatial locality and false sharing, and derives an approach that balances the impact of the two. Experimental results demonstrate that such a balanced approach out-performs those approaches that consider only one of these two issues. On an eight-processor SGI Origin 2000 system, our approach brings an additional 9% improvement over a powerful locality optimization technique that uses both loop and data transformations. Also, our approach obtains an additional 19% improvement over an optimization technique that is oriented specifically toward reducing false sharing. Our study also reveals that in addition to reducing synchronization costs and improving memory subsystem performance, obtaining large granularity parallelism also helps these two optimization techniques, namely, enhancing locality and reducing false sharing, be compatible.

Original languageEnglish (US)
Pages (from-to)203-211
Number of pages9
JournalParallel Architectures and Compilation Techniques - Conference Proceedings, PACT
StatePublished - Dec 1 1999
EventPorceedings of the 1999 International Conference on Parallel Architectures and Compilation Techniques (PACT '99) - Newport Beach, CA, USA
Duration: Oct 12 1999Oct 16 1999

All Science Journal Classification (ASJC) codes

  • Software
  • Theoretical Computer Science
  • Hardware and Architecture


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