Essay on Power Managing Linux

Power Administration from Cpanel Kernel to Android

黃俊維 R97944026 資訊網路與多媒體所 王博榮 R97942139 電信工程研究所

1 . Introduction

Pertaining to normal personal computer, power management (PM) is utilized to reduce power consumption and reduce cooling requirements. Lower electric power consumption means lower warmth dissipation, which in turn increases program stability, and less energy make use of, which helps you to save money and reduces the impact on the environment. For mobile phone device and embedded program device, it's much more essential because the electric batteries is very limited. Nowadays, android phone and iPhone are more and more pervasive. You will discover more and more sensors and I/O in mobile phone device which can be used to improve the effectiveness of PM. The PM must be tuned for new mobile device's need. With this survey, we would like to not only know the power management system used before, but should also compare these the design of Android os PM.

2 . How does power management system operate?

One electricity management regular for computers is ACPI, which supersedes APM. Most recent (consumer) computers include ACPI support. Why ACPI has more benefits than APM? We'll create a brief launch both of them and compare the.

APM (Advanced Power Management) APM includes one or more layers of software that support power management in computers with power controllable hardware. APM defines the hardware impartial software software between hardware-specific power management software and an operating system power managing policy rider. It goggles the

information on the equipment, allowing higher-level software to use APM without any knowledge of the hardware software.

The APM software software specification defines a layered cooperative environment in which applications, operating systems, unit drivers and the APM THE BIOS work together to reduce power consumption. In brief, APM can extend the

life of system batteries and thereby raises productivity and system availableness.

ACPI (Advanced Configuration & Power Interface) The ACPI specification originated to establish market common extremite enabling powerful operating system (OS)-directed motherboard unit configuration and power administration of both equally devices and entire systems. Different from APM, ACPI allows power over power supervision from within the operating system. The previous industry normal for electric power management, APM, is managed at the THE BIOS level. APM is activated when the program becomes idle. The for a longer time the system idles, the much less power it consumes (e. g. display saver or sleep versus suspend). In APM, the operating system does not have knowledge of when the system will change power declares. There are several software program components that ACPI features: A subsystem which regulates hardware claims and functions that may possess previously experienced the THE BIOS configuration These types of states include: Thermal control Motherboard construction Power declares (sleep, suspend) a policy manager, which is application that sits down on top of the operating system and allows end user input for the system guidelines The ACPI also has gadget drivers those control/monitor devices such as a notebook computer battery, SMBus (communication/transmission path) and EC (embedded controller).

Figure 2 . 1

CPI architecture

Determine 2 . a couple of

CPI power state transition diagram

Desk 2 . one particular APM

assessment between APM and ACPI ACPI

um. Control is located in BIOS. o. Uses activity timeouts to determine when should you power down a device um. Bios seldom used in inserted systems to. Makes power-management decisions managing without updating OS or individual applications o. Simply no knowledge away add-in playing cards or new in equipment (e. g. USB, IEEEE 1394)

u. Control divided between THE BIOS and OPERATING-SYSTEM o. Decisions managed throughout the OS. Enables sophisticated electricity policy pertaining to general-purpose computer systems with common purpose usage patterns and hardware to. No familiarity with device-specific specific scenarios (e. g. Need to provide foreseeable response times in order to respond to important events more than extended period) o. Good luck...

References: 1 . Robin Kravets, P. Krishnan, Power management techniques for portable communication, worldwide Conference about Mobile Computing and Networking. installment payments on your Dynamic electric power management pertaining to embedded devices IBM and MontaVista Application Version 1 . 1, The fall of 19, 2002


Robin Kravets, L. Krishnan, Application-driven power management for mobile communication.


Andreas Weissel, Frank Bellosa, Process sail control: event-driven clock your own for dynamic power management.

5. 6. 7.

APM V1. a couple of spec. ACPI, Android Project - Power Managing, ment. html

eight. 9.

Charlie Guo, Android os Power Supervision Matt Hsu, Jim Huang, Power Administration from Cpanel Kernel to Android, 0xlab, 2009.


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