Explicit energy resource management as a first class operating system resource

Energy consumption has recently been widely recognized as a major challenge for computer system design, especially for mobile systems. The energy constraint will often impact the performance of devices as well as applications. To address this problem, previous works focus on improving energy efficiency of hardwires or reducing energy demand of applications. This thesis advocates a new way to look at the energy problem. It is argued that energy should be managed explicitly as a first-class system resource by the OS and energy-saving efforts across the system should be coordinated in order to achieve global energy-related goals.; This thesis proposes the currentcy model as the basic abstraction for the energy resource. It represents an application's right to consume a certain amount of energy within a fixed amount of time. Currentcy is allocated to applications according to their importance and can be spent on any hardware device to pay for the energy consumption of their activities. Through the management of currentcy, including the currentcy allocation to applications, the currentcy consumption scheduling on devices and currentcy payback, energy could be managed explicitly. A currentcy based energy management framework is proposed in this thesis and it is demonstrated that the battery lifetime (and thus the system lifetime) can be extended while the execution of critical applications can be guaranteed.; The energy resource is a special resource with many unique characteristics. It has impact on all applications as well as all devices, and its management is an unified effort from all system components. These characteristics directly affect the design of the management framework and the management policies. In this thesis, an embedded energy model approach is proposed for energy accounting, the currentcy conserving allocation policy is proposed for efficient management and the currentcy centric scheduling policy is proposed to provide prioritized service to applications. Working within the management framework, these policies can enforce the global goals without application cooperation.; In addition to global management and energy quota enforcement, the management framework is also capable of assisting various local energy-saving efforts. A currentcy-based hard disk scheduler is introduced that schedules hard disk accesses by pseudo-economic activities such as bidding, pricing and debiting. It is shown that by exposing currentcy information to the hard disk, energy can be saved by smarter decisions without violating the global goals. The application-OS interaction for better energy management is also discussed in this thesis.; A prototype system, ECOSystem, is implemented based on the Linux kernel on a laptop platform. The currentcy model, the management framework and the management policies are evaluated using a variety of synthetic benchmarks and real applications. Experiment results show the success of the explicit energy management approach in achieving global energy-related goals and in coordinating various energy-saving efforts.