OmniOrder: Directory-based conflict serialization of transactions

Xuehai Qian, Benjamin Sahelices, Josep Torrellas

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

Abstract

Effective execution of atomic blocks of instructions (also called transactions) can enhance the performance and programmability of multiprocessors. Atomic blocks can be demarcated in software as in Transactional Memory (TM) or dynamically generated by the hardware as in aggressive implementations of strict memory consistency. In most current designs, when two atomic blocks conflict, one is squashed- a performance loss that is often unnecessary. To avoid this waste, this paper presents OmniOrder, the first design that efficiently executes conflicting atomic blocks concurrently in a directory-based coherence environment. The idea is to keep only non-speculative data in the caches and, when the cache coherence protocol transfers a line, include in the message the history of speculative updates to the line. The coherence protocol transitions are unmodified. We evaluate OmniOrder with 64-core simulations. In a TM environment, OmniOrder reduces the execution time of the STAMP applications by an average of 18.4% over a scheme that squashes on conflict. In an environment with SC enforcement with speculation, we run 11 programs that implement concurrent algorithms. OmniOrder reduces the programs' execution time by an average of 15.3% relative to a scheme that squashes on conflict. Finally, OmniOrder's communication overhead of transferring the history of speculative updates is negligible.

Original languageEnglish (US)
Title of host publication41st Annual International Symposium on Computer Architecture, ISCA 2014 - Conference Proceedings
PublisherInstitute of Electrical and Electronics Engineers Inc.
Pages421-432
Number of pages12
ISBN (Print)9781479943968
DOIs
StatePublished - 2014
Event2014 ACM/IEEE 41st International Symposium on Computer Architecture, ISCA 2014 - Minneapolis, MN, United States
Duration: Jun 14 2014Jun 18 2014

Publication series

NameProceedings - International Symposium on Computer Architecture
ISSN (Print)1063-6897

Other

Other2014 ACM/IEEE 41st International Symposium on Computer Architecture, ISCA 2014
Country/TerritoryUnited States
CityMinneapolis, MN
Period6/14/146/18/14

ASJC Scopus subject areas

  • Hardware and Architecture

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