Advanced Power Management for Linux operating systems

Article Title: Advanced Power Management for Linux operating systems. Linux is a technology channel of the IT lab in China. Includes basic categories such as desktop applications, Linux system management, kernel research, embedded systems, and open source.

In Windows, we are very familiar with system power management. We can use the advanced power management module of the motherboard to implement functions such as STR and STD. For laptop users, it is more important to use advanced power management to sleep their laptop and save battery resources. The above mentioned functions are implemented on Windows platforms, which may no longer be difficult for us. However, I am afraid few will know about it if I change to Linux. Today we will introduce the implementation of power management in Linux. Since many servers use Linux, the importance of power management becomes very obvious.

There are two Power Management methods in x86 machines: APM (Advanced Power Management, Advanced Power Management) and ACPI (Advanced Configuration and Power Interface, Advanced Configuration and Power Interface ). APM is the old standard, while ACPI provides more flexible interfaces for managing computers and devices. Linux supports these two protocols, but sometimes manual configuration is required. In addition, the two standards cannot run simultaneously. By default, Linux runs ACPI.

APM allows you to put the machine in the Suspend or Standby status and check the battery capacity. ACPI also allows you to independently power off peripherals (such as display, video card, and PCI Bus), giving you more control over power saving. To make the power management function take effect, you need to enable it in the BIOS and Linux core, and load the necessary application software in linux.

Check whether the system supports Power Management

In the newer core, all include the Support for ACPI and APM. Generally, ACPI is activated. Use dmesg to check whether:

Dmesg | egrep-I '(apm | acpi )'

Kernel command line: vga = 274 quiet console = ttyS3, 9600 acpi = no-idleoot =/dev/hda3

ACPI: Core Subsystem version [1, 20010208]

ACPI: Subsystem enabled

ACPI: System firmware supports: C2

ACPI: plvl2lat = 99 plvl3lat = 1001.

ACPI: C2 enter= 1417 C2 exit = 354

ACPI: C3 enter =-1 C3 exit =-1

ACPI: Not using ACPI idle

ACPI: System firmware supports: S0 S1 S4 S5

In addition, the/proc/sys/ACPI directory will be added to systems that support acpi. If it exists, it indicates that the core has loaded the ACPI driver.

Specific Application Instance

We recommend that you use the latest core (for example, 2.4.5 ). Because the old core supports less features, while 2.2.x supports ACPI at the core, there are only a few features.

Advanced Power Management

APM applications include apmd and other applications (such as APM ). We recommend that you go to rpmfind.net to find the latest version suitable for your use. After installing and running OK, we can test the APM command.

The simplest use of APM is to display the battery capacity on the machine.