On the Implication of NTC versus Dark Silicon on Emerging Scale-Out Workloads: The Multi-Core Architecture Perspective

The end of Dennard's scaling poses computer systems, especially the datacenters, in front of both power and utilization walls. One possible solution to combat the power and utilization walls is dark silicon where transistors are under-utilized in the chip, but this will result in a diminishing performance. Another solution is Near-Threshold Voltage Computing (NTC) which operates transistors in the near-threshold region and provides much more flexible tradeoffs between power and performance. However, prior efforts largely focus on a specific design option based on the legacy desktop applications, therefore, lacking comprehensive analysis of emerging scale-out applications with multiple design options when dark silicon and/or NTC are/is applied. In this paper, we characterize different perspectives including performance, energy efficiency and reliability in the context of NTC/dark silicon cloud processors running emerging scale-out workloads on various architecture designs. We find NTC is generally an effective way to alleviate the power challenge over scale-out applications compared with dark silicon, it can improve performance by 1.6X, energy efficiency by 50 percent and the reliability problem can be relieved by ECC. Meanwhile, we also observe tiled-OoO architecture improves the performance by 20~370 percent and energy efficiency by 40~600 percent over alternative architecture designs, making it a preferable design paradigm for scale-out workloads. We believe that our observations will provide insights for the design of cloud processors under dark silicon and/or NTC.