Power management/Processor/ru

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Dynamic frequency scaling

Эта статья описывает настройку управления питанием для процессоров.

Изменение частоты процессора

Изменение частоты процессора — это метод, в котором частота процессора может быть автоматически изменена "на лету" для сохранения энергии, а также это уменьшит количество выделяемого чипом тепла.

Установка

BIOS

Некоторые функции могут быть включены или отключены в BIOS. Убедитесь, что следующие включены:

• "Processor C1E support"
• "Enhanced Speedstep (EIST)"

Ядро

Активируйте следующие параметры ядра:

Ядро Включение параметров ядра для управления питанием

Power management and ACPI options  --->
     [*] ACPI (Advanced Configuration and Power Interface) Support  --->
         <*>   Processor
     CPU Frequency scaling  --->
         [*] CPU Frequency scaling
             Default CPUFreq governor (ondemand)  --->
                 Select a default governor; see below table
                 Default is ondemand
             *** CPU frequency scaling drivers ***
                 Select a driver; see below table

A governor is needed, which is responsible for changing the frequency based on its profile:

Default CPUFreq governor

Option	Module	Supported Processors	Note
'performance' governor	cpufreq_performance	Sets the frequency statically to the highest available CPU frequency.	For Intel core processors, this should be selected as default.
'powersave' governor	cpufreq_powersave	Sets the frequency statically to the lowest available CPU frequency.	Can't be set as default.
'userspace' governor for userspace frequency scaling	cpufreq_userspace	To set the CPU frequency manually or when a userspace program shall be able to set the CPU dynamically.
'ondemand' cpufreq policy governor	cpufreq_ondemand	Does a periodic polling and changes frequency based on the CPU utilization.	For processors other than Intel core, this should be selected as default.
'conservative' cpufreq governor	cpufreq_conservative	Similar to ondemand. The frequency is gracefully increased and decreased rather than jumping to 100% when speed is required.

Заметка
Name of the active CPUFreq governor is available in: /sys/devices/system/cpu/cpu[0-9]*/cpufreq/scaling_governor

CPU frequency scaling drivers

Option	Module	Supported Processors	Note
Intel P state control	intel_pstate	Newer (SandyBridge+) Intel Core
Processor Clocking Control interface driver	pcc-cpufreq
ACPI Processor P-States driver	acpi-cpufreq	Older Intel Core, Intel Atom, Intel Pentium M
AMD Opteron/Athlon64 PowerNow!	powernow-k8	AMD Opteron, AMD Athlon 64, AMD Turion 64
Intel Enhanced SpeedStep (deprecated)	speedstep-centrino	Intel Pentium M (Centrino), Intel Xeon	Deprecated, use ACPI Processor P-States driver instead
Intel Pentium 4 clock modulation	p4-clockmod	Intel Pentium 4, Intel XEON	Causes severe slowdowns and noticeable latencies

Тики

The processor saves the most energy when the processor stays longer in power savings mode, so reduce the amount of ticks that wakes the processor up. Details about the available tickless modes can be found in the kernel documentation.

Установка

BIOS

Некоторые функции могут быть включены или отключены в BIOS. Убедитесь, что следующие включены:

• "HPET"
• "Multimedia timer"

Ядро

Активируйте следующие параметры ядра:

Ядро Включение параметров ядра, которые оптимизируют тик

Processor type and features  --->
   [*] Tickless System (Dynamic Ticks)
   [*] High Resolution Timer Support
   [*] HPET Timer Support

Заметка
Эти параметры теперь находятся в "General setup" -> "Timers subsystem".

PowerTOP

PowerTOP is a utility designed to measure, explain and minimize a computer's electrical power consumption.

When it is run, it sorts the running processes in order of how often they cause the processor to wake up. For details on installation, configuration and usage see the separate PowerTOP article.

Hprofile

It is possible to change the active CPU governor using a simple command:

root #for c in $(ls -d /sys/devices/system/cpu/cpu[0-9]*); do echo ondemand >$c/cpufreq/scaling_governor; done

Прочтите /etc/local.d/README, чтобы узнать, как выполнять эту команду во время загрузки.

Applications such as sys-power/cpupower do little more than the above but with some interface on top of it. However, having to run certain commands as root depending on the system usage is not efficient for most users. It is better to automate some of the decisions of governing CPU frequency. For instance, when not wired to AC power, most users would like to have the system in a power saving mode.

This is where Hprofile comes into play. Please refer to its article for more information and configuration.

Смотрите также

• ACPI — Advanced Configuration and Power Interface (усовершенствованный интерфейс управления конфигурацией и питанием)

Внешние ресурсы

• What exactly is a P-state? (Pt. 1) - An Intel article (kind of) explaining P-states.
• Linux's "Ondemand" Governor Is No Longer Fit - Explains why ondemand should not be used for newer Intel core processors.