Introducing Runahead Threads for SMT Processors

In this paper, we propose Runahead threads on Simultaneous Multithreading processors as a valuable solution for both exploiting the memory-level parallelism and reducing the resource contention. This approach transforms a memory-bounded eager resource thread into a speculative light thread, alleviating critical resource con icts among multiple threads. Furthermore, it improves the threadlevel parallelism by removing long-latency memory operations from the instruction window, and thus it releases busy resources otherwise. We compare an SMT architecture using Runahead threads (SMTRA) to both state-of-the-art static fetch and dynamic resource control policies. Our results show that the SMTRA combination performs better, in terms of throughput and fairness, than any of the other policies.