A DVS-assisted hard real-time I/O device scheduling algorithm

Abstract

The I/O subsystem has become a major source of energy consumption in a hard real-time monitoring and control system. To reduce its energy consumption without missing deadlines, a dynamic power management (DPM) policy must carefully consider the power parameters of a device, such as its break-even time and wake-up latency, when switching off idle devices. This problem becomes extremely complicated when dynamic voltage scaling (DVS) is applied to change the execution time of a task. In this paper, we present COLORS, a composite low-power scheduling framework that includes DVS in a DPM policy to maximize the energy reduction on the I/O subsystem. COLORS dynamically predicts the earliest-access time of a device and switches off idle devices. It makes use of both static and dynamic slack time to extend the execution time of a task by DVS, in order to create additional switchoff opportunities. Task workloads, processor profiles, and device characteristics all impact the performance of a low-power real-time algorithm. We also identify a key Real-Time Syst (2009) 41: 222-255 223 metric that primarily determines its performance. The experimental results show that, compared with previous work, COLORS achieves additional energy reduction up to 20%, due to the efficient utilization of slack time.

Intra-task device scheduling for real-time embedded systems

“…Chu et al [10] proposed a composite low-power scheduling framework called COLORS. COLORS is a Dynamic Voltage Scaling (DVS) assisted I/O device scheduling algorithm for periodic hard RT systems.…”

“…Oðp'Þ. The complexity of COLORS [10] is Oðm'eðln 'eÞÞ þ Oðm' 2 eÞ, where e denotes the ratio of the largest period to the smallest period and m presents the sum of the number of peripheral intervals in all tasks.…”