In K/X/Ubuntu or another Debian-based machine you might just try to
install cpufrequtils (sudo apt-get install cpufrequtils) to get
frequency scaling working. If that does for you then you don't need to
go through the parts of finding and loading the correct modules below.
Just skip to the section on configuring the scaling governor.
Kernel version
Make sure your kernel version is at least 2.6.12 to make use of all
the possible governors that will be mentioned. All of the frequency
scaling will be done with kernel modules and not user space governors.
Enable support in your BIOS
Enter your BIOS and make sure Cool'n'Quiet (AMD) or SpeedStep (Intel)
is enabled for you CPU. Some BIOS's may not have an option for either.
If you don't find the option it is probably enabled by default.
Unfortunately your BIOS may have the option but it is listed as
another name altogether. If that is the case check your BIOS's manual
for more information.
Remove any userspace CPU scaling programs
There are some userspace programs that can be run to scale the
processors frequency. We will be scaling the CPU with the kernel so we
don't need these. So if you have any we are going remove them now. You
may want to look into these as they can be helpful in certain
situations. This article will deal with just using the kernel modules
to scale.
sudo apt-get remove powernowd cpudyn cpufreqd powersaved speedfreqd
Install the module for your CPU
When you installed your system there is a very good chance your CPU
was detected by default and the module you need for for scaling is
already running. Below is a command that will help you identify what
type of processor(s) you have.
cat /proc/cpuinfo
After you know this then you will know what kernel module you will
need to load for it. Here is the command to see what kernel modules
are loaded.
lsmod
Below are CPU descriptions and the commands used to load the kernel
modules based on what processor you have. Look at the output from
lsmod above and use the modules names after the word "modprobe" below
to see if you already have a module loaded. If you do then just move
on to the next step. If not then use the CPU info you found and figure
out which module you need to load. Then run the command to load it.
CPU: PIII-M or P4 without est. 2 module types for this.
sudo modprobe speedstep-ich
or
sudo modprobe speedstep-smi
CPU: Intel Core Duo, Intel Core2 Duo or Quad, or Intel Pentium M. This
has been merged into the acpi-cpufreq module in later kernels.
sudo modprobe speedstep-centrino
CPU: Intel Celeron, Xeon, and Pentium 4 processors
sudo modprobe p4_clockmod
CPU: AMD K6. Socket Type: Socket 7
sudo modprobe powernow-k6
CPU: AMD Sempron/Athlon/MP ( K7 ). Socket Types: A, Slot A.
sudo modprobe powernow-k7
CPU: AMD Duron/Sempron/Athlon/Opteron 64 ( K8 ). Socket Types: 754,
939, 940, S1 ( 638 ), AM2 ( 940 ), F ( 1207 ).
sudo modprobe powernow-k8
CPU: VIA CentaurHauls* or Transmeta GenuineTMx86*
sudo modprobe longhaul
As a last resort if any of these don't work you can try the generic
one for ACPI. More drivers are getting moved to this module in later
kernels like speedstep-centrino after 2.6.20.
sudo modprobe acpi-cpufreq
Inserting the scaling modules
Now that the CPU frequency module is loaded we can now insert the
scaling modules. To see which scaling modules you have a available you
can use this command (using a Bash shell).
ls /lib/modules/$(uname -r)/kernel/drivers/cpufreq
If you have these modules then they may already be running. To check
if they are try the following command.
lsmod | grep freq
If you see most or all of modules that where listed in the cpufreq
directory then your done. Move on to the next section. If not here are
the commands to load the modules.
sudo modprobe cpufreq_conservative cpufreq_ondemand cpufreq_powersave cpufreq_stats cpufreq_userspace freq_table
Now that they are loaded you will want to load them on boot. To do
this on a Debian based system like K/X/Ubuntu put the following lines
in the /etc/modules file. You will have to check on where to put them
on other distros like RedHat (/etc/modules.conf?). Remember to put the
name of your CPU's module (you found above) in here also so it loads
on boot. That is only if it is not loaded on boot. If you did not find
it with lsmod when you first looked then it did not load
automatically.
cpufreq_conservative
cpufreq_ondemand
cpufreq_powersave
cpufreq_stats
cpufreq_userspace
freq_table
Configuring the scaling modules
Now that they are loaded we can configure the governor. First you have
to choose the governor you want to use. Below is a list the governors
and how each works. You can decide which one you fits your needs best.
If the module for a governor is loaded then you can use it. Remember
you can see what modules are loaded with the lsmod command. Commands
are done with sudo below like in K/X/Ubuntu world. You can switch to
root and run the same commands just without the sudo sh -c " " if you
like.
To show the available governors you can use.
sudo cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_governors
Ondemand governor - sets the CPU frequency depending on the current
usage. To do this the CPU must have the capability to switch the
frequency very quickly. This would be good for systems that do a lot
of work (high load) for a short periods of time and then don't do much
(low load) the rest of the time.
sudo sh -c "echo ondemand > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor"
Ondemand governor configuration options
sampling_rate - This is measured in microseconds (one millionth of a
second). This is how often you want the kernel to look at the CPU
usage and to make decisions on what to do about the frequency.
Typically this is set to values of around '10000' or more. If you
wanted to set the sampling rate to 1 second you would set it to
1000000 like in the following example.
sudo sh -c "echo 1000000 > /sys/devices/system/cpu/cpu0/cpufreq/ondemand/sampling_rate"
show_sampling_rate_(min|max) - This is minimum and maximum sampling
rates available that you may set 'sampling_rate' to. I believe in
microseconds also. I've seen discussion on getting rid of this in
later kernels don't count on it being there in the future. To see both
just do the following.
sudo cat /sys/devices/system/cpu/cpu0/cpufreq/ondemand/sampling_rate_min
sudo cat /sys/devices/system/cpu/cpu0/cpufreq/ondemand /sampling_rate_max
up_threshold - This defines what the average CPU usage between the
samplings of 'sampling_rate' needs to be for the kernel to make a
decision on whether or not it should increase the frequency. For
example when it is set to its default value of '80' it means that
between the checking intervals the CPU needs to be on average more
than 80% in use to then decide that the CPU frequency needs to be
increased. To set this to something lower like 20% you would do the
following.
sudo sh -c "echo 20 > /sys/devices/system/cpu/cpu0/cpufreq/ondemand/up_threshold"
ignore_nice_load - This parameter takes a value of '0' or '1'. When
set to '0' (its default), all processes are counted towards the 'cpu
utilization' value. When set to '1', the processes that are run with a
'nice' value will not count (and thus be ignored) in the overall usage
calculation. This is useful if you are running a CPU intensive
calculation on your laptop that you do not care how long it takes to
complete as you can 'nice' it and prevent it from taking part in the
deciding process of whether to increase your CPU frequency. To turn
this on do the following.
sudo sh -c "echo 1 > /sys/devices/system/cpu/cpu0/cpufreq/ondemand/ignore_nice_load"
Conservative governor - CPU frequency is scaled based on current load
of the system. It is similar to ondemand. The difference is that it
gracefully increases and decreases the CPU speed rather than jumping
to max speed the moment there is any load on the CPU. This would be
best used in a battery powered environment.
sudo sh -c "echo conservative > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor"
Conservative governor configuration options
freq_step - This describes what percentage steps the CPU freq should
be increased and decreased smoothly by. By default the CPU frequency
will increase in 5% chunks of your maximum CPU frequency. You can
change this value to anywhere between 0 and 100 where '0' will
effectively lock your CPU at a speed regardless of its load whilst
'100' will, in theory, make it behave identically to the "ondemand"
governor. For example to have it step up and down in increments of 10%
you would do the following.
sudo sh -c "echo 10 > /sys/devices/system/cpu/cpu1/cpufreq/conservative/freq_step"
down_threshold - This is same as the 'up_threshold' found for the
"ondemand" governor but for the opposite direction. For example when
set to its default value of '20' it means that if the CPU usage needs
to be below 20% between samples to have the frequency decreased. For
example to set the down threshold to 30% you would do the following.
sudo sh -c "echo 30 > /sys/devices/system/cpu/cpu0/cpufreq/conservative/down_threshold"
sampling_rate - same as ondemand. sampling_rate_(min|max) - same as
ondemand. up_threshold - same as ondemand. ignore_nice_load - same as
ondemand.
Performance governor - CPU runs at max frequency regardless of load.
This module might not be listed in the running modules but is still
available. My guess is it is built into the kernel for K/X/Ubuntu.
Yours may be the same way.
sudo sh -c "echo performance > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor"
Powersave governor - CPU runs at min frequency regardless of load.
sudo sh -c "echo powersave > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor"
Cpufreq stats about your CPU
The cpufreq module lists stats about your CPU. These will help you
find out things like the current frequency of your processor or what
available frequencies your CPU can scale to. Check them out below.
cpuinfo_cur_freq - Show the current frequency of your CPU(s). You can
also find this out by doing a "cat /proc/cpuinfo".
sudo cat /sys/devices/system/cpu/*/cpufreq/cpuinfo_cur_freq
cpuinfo_max_freq - Show the maximum frequency your CPU(s) can scale
to.
sudo cat /sys/devices/system/cpu/*/cpufreq/cpuinfo_max_freq
cpuinfo_min_freq - Show the minimum frequency your CPU(s) can scale
to.
sudo cat /sys/devices/system/cpu/*/cpufreq/cpuinfo_min_freq
scaling_available_frequencies - Show all the available frequencies
your CPU(s) can scale to.
sudo cat /sys/devices/system/cpu/*/cpufreq/scaling_available_frequencies
scaling_cur_freq - Show the available frequency your CPU(s) are scaled
to currently.
sudo cat /sys/devices/system/cpu/*/cpufreq/scaling_cur_freq
scaling_driver - Show the cpufreq driver the CPU(s) are using.
sudo cat /sys/devices/system/cpu/*/cpufreq/scaling_driver
scaling_max_freq - Set the maximum frequency your CPU(s) are allowed
to scale to. Look at the output from scaling_available_frequencies
above. Then you can pick one of those numbers (frequencies) to set to
be the maximum frequency the CPU(s) will be allowed to scale to. For
example if your CPU output from scaling_available_frequencies was
2000000 1800000 1000000 then you might set this to 1800000. So when
the CPU scales it will only go to a max of 1800000 and not 2000000. An
example on how to set this would be the following.
sudo sh -c "echo 1800000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq"
scaling_min_freq - Same as scaling_max_freq but setting a value that
will not allow the CPU(s) to go below. For example.
sudo sh -c "echo 1800000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq"
Keeping any of your settings for cpufreq on reboot
Since all the settings we have been doing are in the /sys virtual file
system they will not be saved after a reboot. You can go about setting
these on reboot a few ways.
The first way is to put the lines you have been executing in
/etc/rc.local. Since root executes rc.local on boot you don't need to
sudo before each line. Your rc.local could look like the following
example which sets the ondemand governor and the up_threshold to 20%.
Don't forget to make sure the module for your CPU and the cpufreq
scaling modules are set to load on boot also.
echo ondemand > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
echo 20 > /sys/devices/system/cpu/cpu0/cpufreq/ondemand/up_threshold
The second way to keep your settings on reboot is to install
sysfsutils (sudo apt-get install sysfsutils). Then you could add the
following lines to /etc/sysfs.conf which do the same thing as in the
/etc/rc.conf example.
devices/system/cpu/cpu0/cpufreq/scaling_governor=ondemand
devices/system/cpu/cpu0/cpufreq/ondemand/up_threshold=20
Best Answer
You're possbily affected by this bug:
https://bugzilla.kernel.org/show_bug.cgi?id=114551
The patch only landed in the mainline kernel v 4.6. In due course, maybe it'll be backported to 16.04LTS, or in Feb 2017, it should arrive in the next LTS Enablement Stack:
https://wiki.ubuntu.com/Kernel/LTSEnablementStack#Kernel.2FSupport.A16.04.x_Ubuntu_Kernel_Support