Priority based forced requeue to reduce worst-case latencies for bursty traffic

In this paper we introduce priority based forced requeue to decrease worst-case latencies in NoCs offering best effort services. Forced Requeue is to prematurely lift out low priority packets from the network and requeue them outside using priority queues. The first benefit of this approach, applicable to any NoC offering best effort services, is that packets that have not yet entered the network now compete with packets inside the network and hence tighter bounds on admission times can be given. The second benefit - which is more specific to deflective routing as in the Nostrum NoC - is that packet ldquoreshufflingrdquo dramatically reduces the latency inside the network for bursty traffic due to a lowered risk of collisions at the exit of the network. This paper studies the Forced Requeuing on a mesh with varying burst sizes and traffic scenarios. The experimental results show a 50% reduction in worst-case latency from a system perspective thanks to a reshaped latency distribution whilst keeping the average latency the same.