Performance Characterization of Simultaneous Multi-Threading and Index Partitioning for an Online Document Search Application

This work reports on the results of a performance characterization of Simultaneous Multi-Threading (SMT) and Index-Partitioning (IP) when executing an online document search application. One of the key paper findings is that SMT is suitable for a latency sensitive application. In particular, our analysis shows that while SMT degrades single-thread execution latency, it still improves overall response-latency (queueing plus execution latency) because the multiple SMT contexts increase available throughput and help decrease sufficiently queuing latency. SMT is particularly effective in reducing the queueing latency induced by IP. Additionally, we find that in every situation we have evaluated combining SMT and IP yields the same or better average and tail overall response-latency for the application, dataset and server type used in this study. This is true for both single and dual socket server configurations we have evaluated. Our analysis for the dual socket configuration reveals that IP benefits increase with higher utilization. This is in contrast to the typical belief that IP benefits diminish with higher utilization. This is a result of judicious pinning of index-threads and index-data to the hardware to reduce remote memory access.