language: en

Scintilla: Cluster Computing with SCI

Max Ibel, Klaus E. Schauser, Chris J. Scheiman, and Michael Schmitt
Department of Computer Science University of California, Santa Barbara
Santa Barbara, CA 93106
fibel,schauser,chriss,schmittmg@cs.ucsb.edu

Abstract The Scintilla project at UCSB studies SCI-based cluster computing. The Scalable Coherent Interface (SCI) is a recent communication standard for cluster interconnects. We focus on non-coherent SCI, using our cluster setup of SBus-based and PCI-based workstations connected via Dolphin SCI adapters. Our motivation for choosing SCI as network fabric is the very low latency and high bandwidth. We study how to map a variety of programming models efficiently onto the SCI hardware, focusing on message passing and global address space support, implementing Active Messages and Split-C. We present implementation trade-offs, present performance measurements and compare the PCI and SBus adapters. We found that the user-level load/store programming interface of SCI is very convenient to use, achieves low latencies, and is fully virtualized, simultaneously supporting multiple parallel programs and communication channels. On the other hand, neither of the programming models studied maps directly to SCI. Issues such as notification, atomic operations, and virtual address space limitations represent major implementation challenges, which we address with a combination of compiler and run-time support. Overall, we found the SCI network a good substrate for high-performance cluster computing.

1 Introduction