Qthreads: An API for programming with millions of lightweight threads

Large scale hardware-supported multithreading, an attractive means of increasing computational power, benefits significantly from low per-thread costs. Hardware support for lightweight threads is a developing area of research. Each architecture with such support provides a unique interface, hindering development for them and comparisons between them. A portable abstraction that provides basic lightweight thread control and synchronization primitives is needed. Such an abstraction would assist in exploring both the architectural needs of large scale threading and the semantic power of existing languages. Managing thread resources is a problem that must be addressed if massive parallelism is to be popularized. The qthread abstraction enables development of large-scale multithreading applications on commodity architectures. This paper introduces the qthread API and its Unix implementation, discusses resource management, and presents performance results from the HPCCG benchmark.