Idle state

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Crescent moon : Sleep symbol according to IEEE 1621

The hibernation , also known as hibernation (English literally for "winter sleep") and suspend to disk (German for example: "suspend on hard drive "), together with the standby mode ( suspend to RAM ) form two types of energy-saving functions in modern PCs . They are used in particular in notebooks , since the saving of electrical energy when operating without a mains extends the battery life.

Technical details

In the idle state, the computer is put into a largely currentless state by the user so that it can continue working at the same point later. In standby mode, on the other hand, all the parts of the computer that are not required (such as the hard drive) are deactivated or switched off as far as possible in order to reduce the power consumption as far as possible and at the same time to reactivate all required parts as quickly as possible. This means that after work interruptions, user input can be continued at the exact point at which it was previously left off. However, restarting the computer from hibernation is not a restart, as is sometimes necessary after software or system updates.

The technical implementation is carried out with standard x86 PCs via the ACPI status "S4" ("suspend to disk"). If the computer changes to this state, the content of the main memory is written to the hard disk , and almost all system components are electronically switched off. When the computer is reactivated, the image saved on the hard disk is reloaded into the main memory ( RAM ). In addition, the internal states of peripheral devices may have to be restored.

As in the standby mode (ACPI “S3”) (in which the main memory is still supplied with energy), the computer does not shut down completely in the idle state and does not tolerate an error-free total disconnection from the power supply. The use of a power strip with a power switch in order to avoid incurring additional electricity costs requires the system to be set to the ACPI state "S5" ("soft off") beforehand.

Many operating systems such as Linux , Windows and Mac OS offer the option of activating hibernation; Usually the option is initially deactivated.

Designations

Depending on the operating system and language version, the names for hibernation and standby mode are different. For example, “hibernation” can mean something different under Mac OS than under Windows.

technically German English
OS X Windows Xubuntu KDE SC 4 OS X Windows
suspend to RAM (S3) Idle state Standby mode Standby Idle state Sleep Stand By
suspend to disk (S4) Idle state Idle state Idle state Deep sleep Hibernate Hibernate
suspend to RAM and disk Idle state Save energy a Hybrid sleep - Safe sleep Stand by a
aHybrid standby mode from Windows Vista

"Safe Sleep" includes both suspend-to-RAM and suspend-to-disk: the computer saves its state both on the hard disk and in the main memory; the hard disk copy is only used if the power supply is switched off or fails during hibernation , for example through an empty battery.

Windows

At first glance, Windows Vista and 7 only offer the “Energy Save” mode, which is designed as a hybrid mode by default. This means that it uses the advantages of standby mode and hibernation in one function. The mode puts the system into standby mode (usually the state "S3" - "suspend to RAM") and also writes the contents of the main memory to the hard disk or in stationary ReadyDrive and ReadyBoost flash memory. If you disconnect the PC from the power supply and switch it on again later, the computer boots up as if it had been put into sleep mode. Without disconnection from the network, the advantage of the considerably faster reactivation of the computer from standby mode is used. However, it is also possible to reactivate conventional hibernation under Vista and 7. Activation of the idle state is not possible with some devices, e.g. B. on PCs with InstantGo .

Under the Microsoft operating systems Windows ME , Windows 2000 , Windows XP , Windows Vista , Microsoft Windows 7 , Windows 8 / 8.1 and Windows 10 , the file hiberfil.sysis saved by default in the root directory of the system partition . The file hiberfil.sysis the same size as the main memory. Under 32-bit operating systems, hibernation is only supported up to a main memory size of a maximum of 4 GB.

Linux

Gabor Kuti and Pavel Machek developed a first implementation for “hibernation” functionality in Linux for the Linux kernel version 2.2 at the end of the 1990s. This resulted in the kernel module swsusp, which is still partially used in kernel version 2.4 . Later the modules suspend2 , pmdisk and etcsusp were derived from swsusp . Although the kernel developers only maintain uswsusp today, some Linux distributions still use one of the other modules mentioned in their current editions.

All kernel modules responsible for the hibernation functionality work in the same way:

  1. The user or a script calls the hibernation command (can be called both in the command line and from a graphical user interface ).
  2. All running processes is a suspend - Signal sent, so they can continue their activities monitored.
  3. All device interfaces are frozen so that they can no longer change the system status.
  4. A dump of the entire memory is the swap - partition written (Is the swap partition too small preparing the hibernation is interrupted with an error message).
  5. All device interfaces are reactivated.
  6. The system will shut down and turn off normally.

When the system is restarted, the whole kernel is loaded first as usual. Before the swap partition is mounted, this checks whether a hibernation image is stored on it. If he finds one, it is read and written back to the memory. This is done instead of initializing the system services. ( Daemons )

Mac OS

Macs built in mid-1999 switch off the fans, external devices and PCI cards when they are idle (so-called deep sleep ).

The "safe sleep" mode is only possible in newer Macs, all × 86 Macs can use it, with the latest PowerPC Macs it can be activated in the Open Firmware instead of the normal "sleep". The choice between “sleep” and “safe sleep” cannot be controlled via the system settings, but is preset depending on the device type (desktop computer or laptop) and the year of manufacture.

However, it is possible to change this setting using a terminal command. The RAM content is also saved in a file during "safe sleep". If the laptop battery is empty or the power fails during hibernation, the work session can be automatically restored after a restart. If the power supply is not interrupted, the computer wakes up just as quickly as from a simple "sleep".

Web links

Individual evidence

  1. ↑ Shut down the PC or put the PC into hibernation or standby mode. support.microsoft.com
  2. ↑ a b c d Hibernate feature in Linux. Free Software Magazine, accessed March 12, 2012.
  3. ↑ Fine-tuning hibernation - saving power on Macs. ( Memento from November 2, 2013 in the Internet Archive )