The impact of data transfer and buffering alternatives on network interface design

The explosive growth in the performance of microprocessors and networks has created a new opportunity to reduce the latency of fine-grain communication. Microprocessor clock speeds are now approaching the gigahertz range. Network switch latencies have dropped to tens of nanoseconds. Unfortunately, this explosive growth also exposes processor accesses to the network interface (NI) as a critical bottleneck for fine-grain communication. Researchers have proposed several techniques, such as using block loads and stores, user-level DMA, and coherent network interfaces, to alleviate this NI access bottleneck. We systematically identify, examine and evaluate the key parameters that underlie these design alternatives. We classify these parameters into two categories: data transfer and buffering parameters. The data transfer parameters capture how messages are transferred between internal memory structures (e.g. processor caches, main memory) of a computer and a memory bus NI. The buffering parameters capture how and where an NI buffers incoming network messages. We evaluate seven memory bus NIs that we believe capture the essential components of the design space exposed by these data transfer and buffering parameters.