Design And Optimization Of Crossbar Scheduling Algorithm For Network-on-Chip

With the rapid development of integrated circuit and semiconductor technology,the proposal of the NoC which is a new architecture to effectively alleviates the problems that the system on chip which is based on the traditional shared bus architecture appeared bottleneck that can not be solved,the proposal of the Network on chip which is a new architecture to effectively alleviates these problems.The routing node and the crossbar switch are the cores of the high performance IP integrated on the NoC,its corresponding scheduling algorithm influences almost all the performance indicators of the NoC.However,the feature of the traditional scheduling algorithm is equivalent to each port will bring greater delay,especially in real-time service such as voice or streaming media transmission,the network delay is very demanding,and the require of the network throughput is relatively low compared to the delay,at this time,appropriately sacrifice part of the throughput as a cost to improve the delay performance appears is particularly important.Based on the architecture of routing node and crossbar,this paper analyzes the shortcomings of the existing mainstream scheduling algorithm without considering the weight,and the implementation steps of iSLIP algorithm which is originally applied to large-scale switching network.First,according to the characteristics of the three steps in an iteration,only the request step does not require any scheduling,the arbitration is added to the input port request,thus eliminating the accept step,simplifying the two execution steps of request and grant in one iteration.Second,set the priority weights for the virtual channel queue as the length of the queue and the waiting time of first cell in a queue respectively as two ways to describe the priority-based weighting algorithm.Then,after simplifying the performance of two different priority weights,the iSLIP algorithm is further improved by combining the simplified iterative steps with the algorithm based on the weight of queue lengh.Finally,set up the simulation platform BookSim2.0 based on the NoC.The operation mechanism of the simulator and the configuration of the modular parameters are analyzed,and the proposed algorithm is implemented in code.In this paper,the synthetic traffic is used to evaluate the performance of the NoC,in the saturation points,the delay of the simplified iteration algorithm based on the weight of queue length under the uniform flow,decreases 15.3%and 3.0%compared with PIM and iSLIP algorithm,the throughput decreases 9.5%compared with iSLIP algorithm.Under the non-uniforam modes of transpose and tornado flow,the delay decreases 14.6%,14.1%and 9.2%,2.7%compared with PIM and iSLIP algorithms respectively,and the throughput decreases 3.9%and 3.0%compared with iSLIP algorithm.The algorithm delay is reduced by more than 10%,and the throughput rate is less than 10%.The algorithm has good performance and has certain practical application value.