Contention and Queueing in an Experimental Multicomputer: Analytical and Simulation-based Results
Report ID: TR-508-96Author: Fang, Wenjia / Martonosi, Margaret / Felten, Edward W.
Date: 1996-01-00
Pages: 21
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Abstract:
We use two methods, analytic modeling and event-driven simulation, to evaluate the performance of communication in the SHRIMP multicomputer under a variety of workloads. This work has two purposes: to learn about the behavior of the SHRIMP machine, and to explore the tradeoffs between analytic modeling and simulation as performance prediction techniques. We find that the system's performance depends mostly on the behavior of the endpoints; most of the message latency is spent arbitrating for the sender's and receiver's memory buses, and doing DMA transfers of data to and from memory. The raw speed of the network is relatively unimportant. Performance is mainly determined by details of DMA speed, network connectivity, and policies for arbitrating for buses and network links. Even for very simple synthetic benchmark programs, the analytic model and the simulator differ by roughly 10% in their performance predictions. Although we believe the simulator to be more accurate than the model, each method has difficulty accurately representing some feature of the real system. Finally, we observe that each of the two tools was valuable in helping to improve the accuracy of the other.