Approximating Age-Based Arbitration in On-Chip Networks [abstract] (ACM DL, PDF)
Michael M. Lee, John Kim, Dennis Abts, Michael Marty, and Jae W. Lee
Proceedings of the 19th International Conference on Parallel Architectures and Compilation Techniques (PACT), September 2010.

The on-chip network of emerging many-core CMPs enables the sharing of numerous on-chip components. This on-chip network needs to ensure fairness when accessing the shared resources. In this work, we propose providing equality of service (EoS) in future many-core CMPs on-chip networks by leveraging distance, or hop count, to approximate the age of packets in the network. We propose probabilistic arbitration combined with distance-based weights to achieve EoS and overcome the limitation of conventional round-robin arbiter. We describe how nonlinear weights need to be used with probabilistic arbiters and propose three different arbitration weight metrics - fixed weight, constantly increasing weight, and variably increasing weight. By only modifying the arbitration of an on-chip router, we do not require any additional buffers or virtual channels and create a complexity-effective mechanism for achieving EoS.