POSTER - Firestorm: Operating systems for power-constrained architectures

Abstract

Moore's law paved the way for doubling the transistors in the same chip area with every generation. However, with the end of Dennard's scaling, voltage and hence the power draw of transistors is no longer dropping proportionally to size. As a result, modern processors cannot use all parts of the processor simultaneously without exceeding the power limit. This manifests as an increasing proportion of dark silicon [4]. In other words, the compute capacity of current and future processors is and will be over-provisioned with respect to the available power. Power limits are influenced by different factors such as the capacity of power distribution infrastructure, battery supply limits, and the thermal capacity of the system. Power limits in datacenters can arise from underprovisioning power distribution units relative to peak power draw. Energy limits are also dictated by the limited capacity of batteries. However, in many systems, the primary limit comes not from the ability to acquire power, but instead from the ability to dissipate power as heat once it has been used. Thermal limits are dictated by the physical properties of the processor materials and also comfort of the user.Thus, power is limited to prevent processor chips from overheating, which can lead to thermal breakdown. As a result, the maximum performance of a system is limited by its cooling capacity, which determines its ability to dissipate heat. Cooling capacity varies across the computing landscape, from servers with external chilled air to desktops with large fans to laptops to fan-less mobile devices.