Friendly barriers: efficient work-stealing with return barriers

  • Authors:

  • Vivek Kumar;Stephen M. Blackburn;David Grove

  • Affiliations:

  • Australian National University, Canberra, Australia;Australian National University, Canberra, Australia;IBM T.J. Watson Research, New York, NY, USA

  • Venue:
  • Proceedings of the 10th ACM SIGPLAN/SIGOPS international conference on Virtual execution environments
  • Year:
  • 2014

Quantified Score

Hi-index 0.00

Visualization

Abstract

This paper addresses the problem of efficiently supporting parallelism within a managed runtime. A popular approach for exploiting software parallelism on parallel hardware is task parallelism, where the programmer explicitly identifies potential parallelism and the runtime then schedules the work. Work-stealing is a promising scheduling strategy that a runtime may use to keep otherwise idle hardware busy while relieving overloaded hardware of its burden. However, work-stealing comes with substantial overheads. Recent work identified sequential overheads of work-stealing, those that occur even when no stealing takes place, as a significant source of overhead. That work was able to reduce sequential overheads to just 15%. In this work, we turn to dynamic overheads, those that occur each time a steal takes place. We show that the dynamic overhead is dominated by introspection of the victim's stack when a steal takes place. We exploit the idea of a low overhead return barrier to reduce the dynamic overhead by approximately half, resulting in total performance improvements of as much as 20%. Because, unlike prior work, we attack the overheads directly due to stealing and therefore attack the overheads that grow as parallelism grows, we improve the scalability of work-stealing applications. This result is complementary to recent work addressing the sequential overheads of work-stealing. This work therefore substantially relieves work-stealing of the increasing pressure due to increasing intra-node hardware parallelism.