Chasing away RAts: Semantics and evaluation for relaxed atomics on heterogeneous systems

Matthew D. Sinclair, Johnathan Alsop, Sarita V. Adve

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

Abstract

An unambiguous and easy-to-understand memory consistency model is crucial for ensuring correct synchronization and guiding future design of heterogeneous systems. In a widely adopted approach, the memory model guarantees sequential consistency (SC) as long as programmers obey certain rules. The popular data-race-free-0 (DRF0) model exemplifes this SC-centric approach by requiring programmers to avoid data races. Recent industry models, however, have extended such SC-centric models to incorporate relaxed atomics. These extensions can improve performance, but are diffcult to specify formally and use correctly. This work addresses the impact of relaxed atomics on consistency models for heterogeneous systems in two ways. First, we introduce a new model, Data-Race-Free-Relaxed (DRFrlx), that extends DRF0 to provide SC-centric semantics for the common use cases of relaxed atomics. Second, we evaluate the performance of relaxed atomics in CPU-GPU systems for these use cases. We fnd mixed results-for most cases, relaxed atomics provide only a small beneft in execution time, but for some cases, they help signifcantly (e.g., up to 51% for DRFrlx over DRF0).

Original languageEnglish (US)
Title of host publicationISCA 2017 - 44th Annual International Symposium on Computer Architecture - Conference Proceedings
PublisherInstitute of Electrical and Electronics Engineers Inc.
Pages161-174
Number of pages14
ISBN (Electronic)9781450348928
DOIs
StatePublished - Jun 24 2017
Event44th Annual International Symposium on Computer Architecture - ISCA 2017 - Toronto, Canada
Duration: Jun 24 2017Jun 28 2017

Publication series

NameProceedings - International Symposium on Computer Architecture
VolumePart F128643
ISSN (Print)1063-6897

Other

Other44th Annual International Symposium on Computer Architecture - ISCA 2017
CountryCanada
CityToronto
Period6/24/176/28/17

Keywords

  • Data-race-free Models
  • GPGPU
  • Memory consistency
  • Relaxed atomics

ASJC Scopus subject areas

  • Hardware and Architecture

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