Power-aware cpu management in qos-guaranteed systems
Ragunathan Rajkumar, Saowanee Saewong · 2007
The need for power optimization with QoS support is increasingly compelling new CPU management in embedded, mobile and server systems. This is due to the direct impact of limited energy sources and heat dissipation. In addition to traditional low-power design that aims for the highest performance delivery, the new concept of design, which enables hardware-software collaboration to scale down power and performance of hardware whenever the system performance can be relaxed, is gaining importance. In this dissertation, we design and develop and reservation-based CPU scheduling algorithms implemented in the OS layer. Using the knowledge of workload, the framework controls the power-state (active, sleep, etc.) and scales the voltage supply and operating frequency of the processors at context switches. The main goal is to minimize power usage and at the same time maintaining task-QoS guarantees. Two major frameworks are proposed. First, we develop varieties of dynamic voltage scaling (DVS) algorithms for systems using a fixed-priority preemptive scheduling policy such as Deadline Monotonic. We develop different DVS algorithms for different task characteristics such as herd real-time task, multimedia applications and batch/interactive tasks. Second, we design and analyze power-aware hierarchical reservations for systems with hierarchical scheduler support. This framework allows the coexistence of heterogeneous scheduling policies for systems that have concurrent applications with diverse criticality and timing constraints such that a single scheduling policy is not sufficient to satisfy those requirements.