Wormhole Bubble in Torus Networks

Abstract

Typical bubble schemes are flow control algorithms based on virtual cut-through switching. It can avoid deadlock problems without using virtual channels. In this paper, we extend bubble mechanism to wormhole flow control in torus networks, design a non-blocking moveable bubble scheme combined with a false packet protocol. The minimum buffer space required for each input channel is one maximum-sized packet. We compare the performance of various bubble-based schemes with simulation. The results show that moveable bubble scheme can achieve higher throughput and lower latency than existing bubble schemes, and be comparable with dateline technique with two virtual channels. When buffer size is limited and packet-size is fixed, it even has some advantage over dateline, improving accepted rates at saturation more than 10%.