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Power Management

The importance of reducing power consumption is a key concern to provide longer battery life with mobile and embedded devices. By enabling software to take advantage of hardware capability in frequency and voltage scaling, the operating system can optimize the power usage of devices.

This page provides a list of the open source projects currently available for ARM processors as well as other processor architectures.

CpuFreq

CPUFreq is a Linux driver "allowing to change the clock speed of the CPU(s) on the fly. This is a good method to save battery power, because the lower the clock speed is, the less power the CPU consumes". Governors provide a generic interface offering dynamic frequency scaling. There are five governors currently available: ondemand, conservative, userspace, performance and powersave. By observing the current workload of the CPU, a governor states which frequency the CPU should be. Indeed, if you are running a simple text editor there is no need to run at full CPU speed.

CPUFreq has recently been implemented on ARM Realview PB1176 JZF-S board.

CpuIdle

(from Linux Kernel Documentation Tree/cpuidle)
For CPU supporting multiple idle-state, this driver allows Various CPUs today support multiple idle levels that are differentiated by varying exit latencies and power consumption during idle. CpuIdle is a generic in-kernel infrastructure that separates idle policy (governor) from idle mechanism (driver) and provides a generic infrastructure to support independent development of governors and drivers. cpuidle resides under drivers/cpuidle.

LessWatts.org

"LessWatts is about creating a community around saving power on Linux, bringing developers, users, and sysadmins together to share software, optimizations, and tips and tricks." [from lesswatts.org]
This website is dedicated to Intel , but refers to a number of projects or applications looking at power management: PowerTOP?, Tickless Idle, Power Policy Manager, Applications Power Management, Processor Power Management, Power and Performance Measurement, BLTK, Linux ACPI, ACPICA, Power QoS?, Device and Bus Power Management, Display and Graphics Power Saving.

DPM

The DPM project resulted from a collaboration between the IBM Austin Research Lab and MontaVista Software. This project is not so active anymore - most activity refocused to using CPUfreq instead.

-- TurhanOz - 03 Jul 2008
 
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