Impact of the end-system and affinities on the throughput of high-speed flows

Network throughput is scaling-up to higher data rates while processors are scaling-out to multiple cores. In order to optimize high speed data transfer into multicore end-systems, network adapter offloads and performance tuning have received a great deal of attention. However, much of this attention is focused on how to set the tuning parameters and which offloads to select for higher performance and not why they do (or do not) work. In this study we have attempted to address two issues that impact the data transfer performance. First is the impact of the processor core affinity (or core binding) which determines the choice of which processor core or cores handle certain tasks in a network-or I/O-heavy application running on a multicore end-system. Second issue is the impact of Ethernet pause frames which provides a link layer flow control in addition to the end-to-end flow control provided by TCP. The goal of our research is to delve deeper into why these tuning suggestions and this offload exist, and how they affect the end-to-end performance and efficiency of a single, large TCP flow.