THE NEED FOR ADAPTIVE DYNAMIC THREAD SCHEDULING IN SIMULTANEOUS MULTITHREADING

Abstract

Earlier studies on Simultaneous Multithreaded (SMT) architectures showed that performance of a realistic SMT architecture saturates early. This paper addresses our contention that a fixed hardware thread scheduling strategy cannot provide optimal results for various thread combinations. We propose an approach that partially schedules threads in the form of a detector thread at a nominal hardware and software cost. It offers the capability to adaptively switch thread scheduling policies depending on various situations. This article shows that there is much room for performance improvement for our adaptive dynamic thread scheduling approach. The results we have obtained by simulating a realistic SMT architecture show that no single fetch policy may outperform the rest more than 50% of the total time. We show that 27% is approximately the upper-bound of the performance improvement for SMT with eight contexts. This demonstrates that our approach may significantly improve performance with good low-throughput detection and fetch policy selection heuristics.