Phase-guided Thread-to-core Assignment for Improved Utilization of Performance-Asymmetric Multi-Core Processors

By: Tyler Sondag and Hridesh Rajan

Abstract

CPU vendors are starting to explore trade offs between die size, number of cores on a die, and power consump- tion leading to performance asymmetry among cores on a single chip. For efficient utilization of these performance- asymmetric multi-core processors, application threads must be assigned to cores such that the resource needs of a thread closely matches resource availability at the assigned core. This significantly complicates the task of an average pro- grammer. The contribution of this work is a technique for automatically determining the mapping between threads and performance-asymmetric cores of a processor. Our ap- proach, which we call phase-guided thread-to-core assign- ment, builds on a well-known insight that programs exhibit phase behavior. We first take code sections and group them into clusters such that each section in a cluster is likely to exhibit similar runtime characteristics. The key idea is that with this clustering, characteristics of a small number of representative sections in a cluster give insight into the be- havior of the entire cluster. Thus the exhibited characteris- tics of the representative sections on different types of cores can be used for automating thread-to-core assignment at a lower runtime cost. Variations of our technique show up to an average 150% improvement in throughput over the stock Linux scheduler for systems with a constant feed of jobs, while maintaining comparable fairness and efficiency.

ACM Reference

Sondag, T. and Rajan, H. 2009. Phase-guided Thread-to-core Assignment for Improved Utilization of Performance-Asymmetric Multi-Core Processors. IWMSE ’09: Proceedings of the 2nd International Workshop on Multicore Software Engineering (May 2009).

BibTeX Reference

@inproceedings{sondag2009phase,
  author = {Tyler Sondag and Hridesh Rajan},
  title = {Phase-guided Thread-to-core Assignment for Improved Utilization of Performance-Asymmetric Multi-Core Processors},
  booktitle = {IWMSE '09: Proceedings of the 2nd International Workshop on Multicore Software Engineering},
  location = {Vancouver, Canada},
  month = {May},
  year = {2009},
  entrysubtype = {workshop},
  abstract = {
    CPU vendors are starting to explore trade offs between die size, number of
    cores on a die, and power consump- tion leading to performance asymmetry among
    cores on a single chip. For efficient utilization of these performance-
    asymmetric multi-core processors, application threads must be assigned to
    cores such that the resource needs of a thread closely matches resource
    availability at the assigned core. This significantly complicates the task of
    an average pro- grammer. The contribution of this work is a technique for
    automatically determining the mapping between threads and
    performance-asymmetric cores of a processor. Our ap- proach, which we call
    phase-guided thread-to-core assign- ment, builds on a well-known insight that
    programs exhibit phase behavior. We first take code sections and group them
    into clusters such that each section in a cluster is likely to exhibit similar
    runtime characteristics. The key idea is that with this clustering,
    characteristics of a small number of representative sections in a cluster give
    insight into the be- havior of the entire cluster. Thus the exhibited
    characteris- tics of the representative sections on different types of cores
    can be used for automating thread-to-core assignment at a lower runtime cost.
    Variations of our technique show up to an average 150% improvement in
    throughput over the stock Linux scheduler for systems with a constant feed of
    jobs, while maintaining comparable fairness and efficiency.
  }
}