CPU frequency scaling - Revision history

NeYurii at 13:09, 19 September 2025

2025-09-19T13:09:12Z

← Older revision		Revision as of 13:09, 19 September 2025
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	In order to check which governors are available for your processors:		In order to check which governors are available for your processors:
	~~<pre>~~		{{cmd\|cat /sys/devices/system/cpu/cpufreq/policy*/scaling_available_governors}}
	cat /sys/devices/system/cpu/cpufreq/policy*/scaling_available_governors
	~~</pre>~~

	To e.g. change the governor of processor 0 to <samp>ondemand</samp>:		To e.g. change the governor of processor 0 to <samp>ondemand</samp>:
	~~<pre>~~		{{cmd\|echo ondemand > /sys/devices/system/cpu/cpufreq/policy0/scaling_governor}}
	echo ondemand > /sys/devices/system/cpu/cpufreq/policy0/scaling_governor
	~~</pre>~~

	To see that the governor you chose works as expected, you may compare <samp>scaling_cur_freq</samp> to <samp>scaling_min_freq</samp> and <samp>scaling_max_freq</samp> for different system loads. All of these files are located in the same folder <samp>/sys/devices/system/cpu/cpufreq/policy0</samp> as the governor settings above.		To see that the governor you chose works as expected, you may compare <samp>scaling_cur_freq</samp> to <samp>scaling_min_freq</samp> and <samp>scaling_max_freq</samp> for different system loads. All of these files are located in the same folder <samp>/sys/devices/system/cpu/cpufreq/policy0</samp> as the governor settings above.
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	== Manipulating the governor ==		== Manipulating the governor ==
	Some governors can be configured further; these settings can be found in the folders <samp>/sys/devices/system/cpu/cpufreq/*</samp>. For instance, the <samp>ondemand</samp> governor defaults to switching to a higher frequency when the CPU usage increases beyond 95%. If we wish to lower this threshold to e.g. 80%, we could run:		Some governors can be configured further; these settings can be found in the folders <samp>/sys/devices/system/cpu/cpufreq/*</samp>. For instance, the <samp>ondemand</samp> governor defaults to switching to a higher frequency when the CPU usage increases beyond 95%. If we wish to lower this threshold to e.g. 80%, we could run:
	~~<pre>~~		{{cmd\|echo 80 > /sys/devices/system/cpu/cpufreq/ondemand/up_threshold}}
	echo 80 > /sys/devices/system/cpu/cpufreq/ondemand/up_threshold
	~~</pre>~~

	== Automatic configuration ==		== Automatic configuration ==
	Once we have found a governor that we are satisfied with, we might want to keep it when the system is rebooted. This can be done by ~~creating a local service in <samp>/etc/local.d</samp>. First, create a new local service <samp>/etc/local.d/cpufreq.start</samp> with the relevant CPU frequency scaling commands discussed above~~:		Once we have found a governor that we are satisfied with, we might want to keep it when the system is rebooted. This can be done by using cpupower package:
			{{cmd\|apk add {{pkg\|cpupower}}}}

	<~~pre~~>		Edit file /etc/conf.d/cpupower to configure required governor with START_OPTS and SYSFS_EXTRA:
	~~#!/bin/sh~~		{{cat\|/etc/conf.d/cpupower\|<nowiki># Set the governor to ondemand for all processors
			START_OPTS="--governor ondemand"

	# ~~Set~~ the ~~governor~~ to ondemand ~~for all processors~~		# Reduce the boost threshold to 80%
	~~for cpu in /sys/devices/system/cpu/cpufreq~~/~~policy*; do~~		SYSFS_EXTRA="ondemand/up_threshold=80"
	~~echo ondemand~~ > ~~${cpu~~}~~/scaling_governor~~		</nowiki>}}
	~~done~~

	~~# Reduce~~ the ~~boost threshold to 80%~~		Start the cpupower daemon using the standard [[OpenRC]] commands:
	~~echo 80 > /sys/devices/system/cpu/cpufreq/ondemand/up_threshold~~		{{cmd\|rc-update add cpupower && rc-service cpupower start}}
	~~</pre>~~

	~~Make the boot script executable~~, ~~make sure local services are started at boot, and sync your changes:~~		Now, CPU frequency scaling is enabled and will be preserved after rebooting.
	~~<pre>~~
	~~chmod +x /etc/local.d/cpufreq.start~~
	~~rc-update add local default~~
	~~lbu commit~~
	~~</pre>~~
	~~Reboot your computer, and~~ CPU frequency scaling ~~should~~ be ~~enabled automatically~~.

	[[Category:Power Management]]		[[Category:Power Management]]

John3-16: Categorized: Power Management

2017-09-19T01:42:49Z

Categorized: Power Management

← Older revision		Revision as of 01:42, 19 September 2017
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	</pre>		</pre>
	Reboot your computer, and CPU frequency scaling should be enabled automatically.		Reboot your computer, and CPU frequency scaling should be enabled automatically.

			[[Category:Power Management]]

John3-16 at 01:40, 19 September 2017

2017-09-19T01:40:01Z

← Older revision		Revision as of 01:40, 19 September 2017
Line 71:		Line 71:
	</pre>		</pre>
	Reboot your computer, and CPU frequency scaling should be enabled automatically.		Reboot your computer, and CPU frequency scaling should be enabled automatically.

	~~[[Category:Power Management]]~~

John3-16: Categorized: Power Management

2017-09-19T00:36:12Z

Categorized: Power Management

← Older revision		Revision as of 00:36, 19 September 2017
Line 71:		Line 71:
	</pre>		</pre>
	Reboot your computer, and CPU frequency scaling should be enabled automatically.		Reboot your computer, and CPU frequency scaling should be enabled automatically.

			[[Category:Power Management]]

Jabirali: Wrote a guide to setting up CPU frequency scaling

2017-06-23T17:43:40Z

Wrote a guide to setting up CPU frequency scaling

New page

''CPU frequency scaling'' is a feature of many modern processors whereby the CPU frequency can be changed at runtime. In this way, the system can be optimized for either powersaving (minimal frequency), performance (maximal frequency), or a combination (automatic switching). The latter would e.g. be optimal for a server that is idle for most of its uptime, but must sustain high CPU throughput when it does receive requests.

== Electing a governor ==
The CPU frequency scaling is handled by a so-called ''CPU governor'', which decides which frequencies to use and when to switch between them. The most common governors are the following:

{| cellpadding="5" border="1" class="wikitable"
|-
! Governor
! Frequency
! Switching
|-
| <samp>performance</samp>
| Maximum
| None
|-
| <samp>powersave</samp>
| Minimum
| None
|-
| <samp>ondemand</samp>
| Automatic
| Immediate
|-
| <samp>conservative</samp>
| Automatic
| Gradual
|-
| <samp>userspace</samp>
| Custom
| Custom
|}

In order to check which governors are available for your processors:
<pre>
cat /sys/devices/system/cpu/cpufreq/policy*/scaling_available_governors
</pre>

To e.g. change the governor of processor 0 to <samp>ondemand</samp>:
<pre>
echo ondemand > /sys/devices/system/cpu/cpufreq/policy0/scaling_governor
</pre>

To see that the governor you chose works as expected, you may compare <samp>scaling_cur_freq</samp> to <samp>scaling_min_freq</samp> and <samp>scaling_max_freq</samp> for different system loads. All of these files are located in the same folder <samp>/sys/devices/system/cpu/cpufreq/policy0</samp> as the governor settings above.

== Manipulating the governor ==
Some governors can be configured further; these settings can be found in the folders <samp>/sys/devices/system/cpu/cpufreq/*</samp>. For instance, the <samp>ondemand</samp> governor defaults to switching to a higher frequency when the CPU usage increases beyond 95%. If we wish to lower this threshold to e.g. 80%, we could run:
<pre>
echo 80 > /sys/devices/system/cpu/cpufreq/ondemand/up_threshold
</pre>

== Automatic configuration ==
Once we have found a governor that we are satisfied with, we might want to keep it when the system is rebooted. This can be done by creating a local service in <samp>/etc/local.d</samp>. First, create a new local service <samp>/etc/local.d/cpufreq.start</samp> with the relevant CPU frequency scaling commands discussed above:

<pre>
#!/bin/sh

# Set the governor to ondemand for all processors
for cpu in /sys/devices/system/cpu/cpufreq/policy*; do
echo ondemand > ${cpu}/scaling_governor
done

# Reduce the boost threshold to 80%
echo 80 > /sys/devices/system/cpu/cpufreq/ondemand/up_threshold
</pre>

Make the boot script executable, make sure local services are started at boot, and sync your changes:
<pre>
chmod +x /etc/local.d/cpufreq.start
rc-update add local default
lbu commit
</pre>
Reboot your computer, and CPU frequency scaling should be enabled automatically.