A linux implementation of the energy-based fair queuing scheduling algorithm for battery-limited mobile systems

This paper provides a concrete implementation and comprehensive assessment of the energy-based fair queuing (EFQ) scheduling algorithm based on the Linux operating system. EFQ is an extended application of the classical fair queuing algorithm in the energy domain. It is designed to provide proportional power sharing as well as effective time-constraint compliance in energy-centric power management (PM) schemes, a type of operating system-level PM schemes that are targeted at providing a battery lifetime guarantee for energy-limited mobile systems. In this paper work, the structure of the Linux completely fair scheduler (CFS) has been effectively utilized to ease the EFQ implementation and reduce the scheduling overhead. Around 150 lines of code have been added to the Linux kernel V3.3 to achieve the EFQ-related functions and to implement the system calls that are required by the Linux user space. To assess the properties of the EFQ scheduler, a test-bench based on the POSIX threads has been developed and the benchmarks of an open-source embedded suite are referred to program the threads under test. The EFQ algorithm is assessed from two aspects, energy management and real-time scheduling. Experimental results on energy management show that EFQ is more effective than the CFS scheduler in managing energy and it can achieve a proportional share of the system power regardless of on which device the energy is spent. Experimental results on real-time scheduling demonstrate that EFQ can achieve strict time-constraint compliance and a robust response time upon the increase of energy estimation error and active tasks.