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Several messaging software architectures (MSAs) have been proposed that entirely remove the operating system from the critical communication path, providing direct user-level access to the network interface and avoiding excessive data copying. In this paper we discuss the most important design issues and tradeoffs related to the functionality and performance of MSAs: the communication model, DMA versus programmed I/O transfers, data copying and protection, message pipelining, message arrival notification, and reliability. In order to illustrate how these issues and tradeoffs are tackled in modern systems, we survey a large number of recently proposed MSAs for the Myrinet interconnection network, including AM, FM, U-Net, VMMC, BIP, PM, and Trapeze.
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