Buffer sizing for QoS flows in wormhole packet switching NoCs

Leonel Tedesco, Fernando Moraes, Ney Calazans
2007 Proceedings of the 20th annual conference on Integrated circuits and systems design - SBCCI '07  
Networks on chip (NoCs) are communication infrastructures that offer parallelism and scalability. Most NoC designs employ wormhole packet switching, since this switching mode optimizes the use of NoC resources. However, this mode may introduce jitter, possibly producing packet loss, due to the violation of temporal QoS constraints. One technique to deal with jitter is to introduce a decoupling buffer (D-buffer) on the target IP. This buffer receives data from the NoC with jitter, while the
more » ... t IP consumes data from this buffer at the application rate, without jitter. Two problems must be solved to implement D-buffers: (i) which size must the buffer have? (ii) how much buffer space should be filled before data consumption starts (threshold)? This work proposes a general method to define D-buffer size and threshold, considering the influence of packaging, arbitration, routing and concurrency between flows. Before presenting the method, the paper extends a previous traffic model for stream applications and characterizes jitter sources in wormhole packet switching. The experimental results obtained with the proposed method showed that simple traffic models employing constant frame sizes result in small D-buffers. On the other hand, employing video frames from application traces (i.e. real application data) increases buffer size and threshold, still suppressing jitter. Application traces highlight the threshold parameter importance.
doi:10.1145/1284480.1284513 dblp:conf/sbcci/TedescoMC07 fatcat:xu5dcih5hzbq7fsc6dblcqdesq