Semantic locality and context-based prefetching using reinforcement learning

Leeor Peled, Shie Mannor, Uri Weiser, Yoav Etsion

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

Abstract

Most modern memory prefetchers rely on spatio-temporal locality to predict the memory addresses likely to be accessed by a program in the near future. Emerging workloads, however, make increasing use of irregular data structures, and thus exhibit a lower degree of spatial locality. This makes them less amenable to spatio-temporal prefetchers. In this paper, we introduce the concept of Semantic Locality, which uses inherent program semantics to characterize access relations. We show how, in principle, semantic locality can capture the relationship between data elements in a manner agnostic to the actual data layout, and we argue that semantic locality transcends spatio-temporal concerns. We further introduce the context-based memory prefetcher, which approximates semantic locality using reinforcement learning. The prefetcher identifies access patterns by applying reinforcement learning methods over machine and code attributes, that provide hints on memory access semantics. We test our prefetcher on a variety of benchmarks that employ both regular and irregular patterns. For the SPEC 2006 suite, it delivers speedups as high as 2.8X (20% on average) over a baseline with no prefetching, and outperforms leading spatio-temporal prefetchers. Finally, we show that the context-based prefetcher makes it possible for naive, pointer-based implementations of irregular algorithms to achieve performance comparable to that of spatially optimized code.

Original languageEnglish
Title of host publicationISCA 2015 - 42nd Annual International Symposium on Computer Architecture, Conference Proceedings
Pages285-297
Number of pages13
ISBN (Electronic)9781450334020
DOIs
StatePublished - 13 Jun 2015
Event42nd Annual International Symposium on Computer Architecture, ISCA 2015 - Portland, United States
Duration: 13 Jun 201517 Jun 2015

Publication series

NameProceedings - International Symposium on Computer Architecture
Volume13-17-June-2015

Conference

Conference42nd Annual International Symposium on Computer Architecture, ISCA 2015
Country/TerritoryUnited States
CityPortland
Period13/06/1517/06/15

All Science Journal Classification (ASJC) codes

  • Hardware and Architecture

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