Interference-aware Incoming Message Detection for MPI Threaded Progression

To enable overlap of computation and communication with non-blocking collective communication, it is required to progress asynchronously a sequence of communications. One of the naive implementation is to use a separate thread for communitation and run it in back of computation thread. However if the total number of threads is greater than the number of physical cores, context switches cause performance degradation of the computation thread. Simultaneous MultiThread (SMT) can be used to avoid this problem. However, commonly-used busy polling for incoming message detection also causes performance degradation of the computation thread. In this paper, we propose incoming message detection method using MONITOR/MWAIT instructions to reduce the performance degradation. Experiment results show that the performance of computation thread is improved largely compared to the busy polling method while latency is suppressed by a small increase.