Florian Schmaus, Nicolas Pfeiffer, Wolfgang Schröder-Preikschat, Timo Hönig, J. Nolte
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引用次数: 4
摘要
在当今的多核和多核处理器中有效地使用并行性是一个持续的挑战。随着在数据中心和嵌入式领域中运行的多核心系统中处理元素数量的快速增长,可扩展性变得比以往任何时候都更加重要。保证可伸缩性通常通过使用完全严格的fork/join并发性来确保,这是Cilk等并发平台使用的流行方法。由于运行时中数据结构的复杂交互,这些平台使用的运行时系统通常采用基于锁的同步。但是,锁定严重限制了可伸缩性。随着具有数百个逻辑核心的商用现成系统的可用性,这正在成为越来越多系统面临的问题。本文提出了一种新的无等待方法Nowa,用于仲裁并发平台运行时系统管理的大量并发链。无等待方法是通过利用完全严格的fork/join并发性的固有属性来实现的,因此可能适用于并发平台的每个窃取延续的运行时系统。我们已经实现了Nowa,并将其与现有的运行时系统(包括Cilk Plus和Threading Building Blocks (TBB))进行了比较,后者采用了基于锁的方法。我们的评估结果表明,在具有256个硬件线程的系统上,与基于锁的实现相比,无等待实现的性能提高了1.64倍。性能平均提升1.17倍,只有一个基准测试出现性能回归。与使用Clang的libomp的OpenMP任务相比,Nowa的平均性能比OpenMP高出8.68倍。
Nowa: A Wait-Free Continuation-Stealing Concurrency Platform
It is an ongoing challenge to efficiently use parallelism with today’s multi- and many-core processors. Scalability becomes more crucial than ever with the rapidly growing number of processing elements in many-core systems that operate in data centres and embedded domains. Guaranteeing scalability is often ensured by using fully-strict fork/join concurrency, which is the prevalent approach used by concurrency platforms like Cilk. The runtime systems employed by those platforms typically resort to lock-based synchronisation due to the complex interactions of data structures within the runtime. However, locking limits scalability severely. With the availability of commercial off-the-shelf systems with hundreds of logical cores, this is becoming a problem for an increasing number of systems.This paper presents Nowa, a novel wait-free approach to arbitrate the plentiful concurrent strands managed by a concurrency platform’s runtime system. The wait-free approach is enabled by exploiting inherent properties of fully-strict fork/join concurrency, and hence is potentially applicable for every continuation-stealing runtime system of a concurrency platform. We have implemented Nowa and compared it with existing runtime systems, including Cilk Plus, and Threading Building Blocks (TBB), which employ a lock-based approach. Our evaluation results show that the wait-free implementation increases the performance up to 1.64× compared to lock-based ones, on a system with 256 hardware threads. The performance increased by 1.17× on average, while no but one benchmark exhibited performance regression. Compared against OpenMP tasks using Clang’s libomp, Nowa outperforms OpenMP by 8.68× on average.