摘要： Cache一致性协议对系统性能和带宽需求具有重要影响,而当前广泛采用的广播协议带宽需求较高,目录协议访存延迟较大,均不适用于国产服务器CPU直连接口带宽较低及延迟较大的应用场景。针对上述问题,基于Token广播协议和目录协议,设计混合一致性协议,采用Simics结合GEMS搭建多路直连片上多核处理器仿真系统,通过运行SPLASH-2测试协议的相关性能。实验结果表明,混合协议的系统性能优于目录协议,与Token协议相比,混合协议以较小的性能代价,大幅降低片间通信带宽需求,且在带宽资源受限系统中具有更好的系统性能。

关键词: 片间直连, Cache一致性, Token协议, 目录协议, 混合协议

Abstract: Cache coherence protocol impacts the system performance and the demand of bandwidth.Snoopy protocols and directory protocols are widely used in modern server systems,but the former needs large bandwidth while the latter has long latency,so they are not suitable for domestic server CPU used in the scenario that the bandwidth is relatively small and latency is relatively long.To solve this problem,this paper proposes a hybrid coherence protocol based on Token protocol and directory protocol,and uses Simics and GEMS to construct a system in which multi-channel Chip Multi-processors(CMP) are directly connected.It then runs SPLASH-2 benchmark to test related performance.The experimental results show that the hybrid protocol has better performance than the directory protocol.Compared with the Token protocol,the hybrid protocol significantly reduces the demand of inter-chip bandwidth at relatively little cost of performance,and has better performance in the system that the bandwidth is not sufficient.

Key words: direct connection among chips, Cache coherence, Token protocol, directory protocol, hybrid protocol

中图分类号: 

• TP332