PULL: ParaStation user-level communication. Design and overview

Abstract

PULL is a user-level communication library for workstation clusters. PULL provides a multi-user, multi-programming communication library for user level communication on top of high-speed communication hardware. In this paper, we describe the design of the communication subsystem, a first implementation on top of the ParaStation communication card, and benchmark results of this first implementation. PULL removes the operating system from the communication path and offers a multi-process environment with user-space communication. Additionally, we have moved some operating system functionality to the user level to provide higher efficiency and flexibility. Message demultiplexing, protocol processing, hardware interfacing, and mutual exclusion of critical sections are all implemented in user-level. PULL offers the programmer multiple interfaces including TCP user-level sockets, MPI [CGH94], PVM [BDG⁺93], and Active Messages [CCHvE96]. Throughput and latency are close to the hardware performance (e.g., the TCP socket protocol has a latency of less than 9 μs).