A scalable flow control algorithm for the Fast Messages communication library

The evolution of the Fast Messages (FM) communication library has shown the importance of flow control to deliver the raw hardware performance of currently available interconnection networks to the applications. However, the credit-based solution used in FM to provide flow control, though simple and efficient for systems of limited dimension, does not scale well when the dimension of the parallel system increases. In this paper, we propose an extension to the FM flow control algorithm where credits can be assigned on-demand to communicating nodes. The experimental results reported in the paper demonstrate that the performance of this new scheme is virtually insensitive to system dimension providing that messages are long enough and there are not communication hot spots in the system. In presence of more general communication patterns, the proposed dynamic credit assignment mechanism can be used to implement adaptive credit allocation policies.