Quantifying the Impact of Architectural Scaling on Communication
Taliver Heath, Samian Kaur, Richard P. Martin, Thu D. Nguyen taliver,rmartin,tdnguyen @cs.rutgers.edu, samian@caip.rutgers.edu Technical Report DCS-TR-418 Department of Computer Science Rutgers University, Piscataway, NJ 08854-8019 Appears in Proceedings of the High Performance Computer Architecture Conference (HPCA), January 2001.
Abstract
This work quanties how persistent increases in processor speed compared to I/O speed reduce the performance gap between specialized, high performance messaging layers and general purpose protocols such as TCP/IP and UDP/IP. The comparison is important because specialized layers sacrice considerable system connectivity and robustness to obtain increased performance. We rst quantify the scaling effects on small messages by measuring the LogP performance of two Active Message II layers, one running over a specialized VIA layer and the other over stock UDP as we scale the CPU and I/O components. We then predict future LogP performance by mapping the LogP model's network parameters, particularly overhead, into architectural components. Our projections show that the performance benet afforded by specialized messaging for small messages will erode to a factor of 2 in the next 5 years. Our models further show that the performance differential between the two approaches will continue to erode without a radical restructuring of the I/O system. For long messages, we quantify the variable per-page instruction budget that a zero-copy messaging approach has for page table manipulations if it is to outperform a single-copy approach. Finally, we conclude with an examination of future I/O advances that would result in substantial improvements to messaging performance.
1. Introduction
This work considers the impact of expected architectural trends on messaging performance. In recent years, much research has focused on the design and implementation of specialized messaging systems [6, 36, 42, 45], reducing the xed cost of sending and receiving messages to tens of instructions and a handful of bus operations. Increased performance, however, is typically gained only by trading off connectivity – the variety and number of potential entities a given messaging system can send to and re1

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