Application-Driven End-to-End Traffic Predictions for Low Power NoC Design

As chip multiprocessors keep increasing the number of cores on the chip, the network-on-chip (NoC) technology is becoming essential for interconnecting the cores. While NoCs result in noticeable performance boost over conventional bus systems, they consume a non-negligible fraction of the system power. One promising solution is to dynamically adjust the working frequencies/voltages of the switches as well as the links between switches in the NoC to match the traffic flows. The question is when to adjust and by how much. Most previous works take a passive approach by reacting to fluctuations in local traffic flows. Unfortunately, this approach may be too slow and too conservative in adjusting the working frequencies/voltages. Since applications often exhibit periodic behaviors, we propose a hardware mechanism to proactively adjust the frequencies/voltages of switches and/or links in NoC by predicting the application runtime traffic. The evaluations show that our design achieves 86% dynamic power savings of the links in the on-chip network, and the resulting overheads from mispredictions are tolerable.