An efficient virtual system clock for the wireless raspberry pi computer platform

摘要

The use of Dynamic Voltage and Frequency Scaling (DVFS) by Energy-Efficient (EE) computer systemsrnconsiderably increases the requirements regarding the design of efficient system clocks. On the one hand,rnthe operation of a system clock must support the independent operating frequencies of the processor corernunits, the dynamic migration of the running processes between the processors core units, and the use ofrnsynchronization and time interpolation techniques to maintain the accuracy of the system clock. On thernother hand, an efficient system clock has to minimize the overhead of its own operation, aiming at energyrnefficiency of EE computer systems.rnIn this paper, we present the design and evaluation of the RVEC virtual system clock for the EE WirelessrnRaspberry Pi (RasPi) platform. In the RasPi platform, the use of DVFS for reducing the energy consumptionrnhinders the direct use of the cycle count of the ARM11 processor core for building an efficient systemrnclock. Therefore, a distinct feature of RVEC is to obviate this obstacle, such that it can make use of therncycle count circuit for precise and accurate time measurements, concurrently with the use of DVFS by thernoperating system of the ARM11 processor core. Specifically, this paper presents the design and experimentalrnevaluation of an implementation of the RVEC virtual system clock in the Linux kernel of the RasPi platformrnwith DVFS. Our experimental results validate the RVEC virtual system clock as an efficient system clockrnfor the EE RasPi platform that runs the Linux operating system.