If it is software-based e. The following processors for the sparc64 architecture are supported by. If the driver requires governor tunables to be per-policy, they are located in a subdirectory of each policy directory. If you did not find it with lsmod when you first looked then it did not load automatically. More drivers are getting moved to this module in later kernels like speedstep-centrino after 2.

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We will be scaling the CPU with the kernel so we don’t need these.

The only values that can be written to this file are 0 and 1. The worker routine of this governor has to run in process context, so it is invoked asynchronously via a workqueue and CPU P-states are updated from there if necessary.

Scaling governors are attached to policy objects and different policy objects can be handled by different scaling governors at the same time although that may lead to suboptimal results in some cases. This may be useful if there are tasks in ad system that should not be taken into account when deciding what frequency to and the CPUs at.

acpi-cpufreq: Add support for modern AMD CPUs

They are expected to carry out computations needed to determine the P-state to use xmd the given policy going forward and to invoke the scaling driver to make changes to the hardware in accordance with the P-state selection. Some CPU frequency scaling – capable processor switch between various. Scaling drivers talk to the hardware. It estimates the CPU load in the cpufdeq way as the ondemand governor described above, but the CPU frequency selection algorithm implemented by it is different.


Yum RPM and apt-get dpkg are 2 very popular ones.

acpi-cpufreq: Add support for modern AMD CPUs []

Powersave governor – CPU runs at min frequency regardless of load. When you installed your system there is a very good chance your CPU was detected by default and ams module you need for for scaling is already running. Otherwise, the frequency will not be changed.

In either case the name of the subdirectory containing the governor tunables is the name of the governor providing them. To check if they are mad the following command. If the module for a governor is loaded then you can use it.

To see which scaling modules you have a available you can use this command using a Bash shell. Ondemand governor – sets the CPU frequency depending on the current usage. Remember you can see what modules are loaded cputreq the lsmod command.

Written by Michael Larabel in Software on 21 August Here are some notes on getting CPU frequency scaling pcufreq on Linux. The time it takes to switch the CPUs belonging to this policy from one P-state to another, in nanoseconds.

That design is based on the observation that the information used by performance scaling algorithms for P-state selection can be represented in a platform-independent form in the majority of cases, so it should be possible to use the same performance scaling algorithm implemented in exactly the same way regardless of which scaling driver is used.

The policy objects created during CPU initialization and other data structures associated with them are torn down when the scaling driver is unregistered which happens when the kernel module containing it is unloaded, for example or when the last CPU belonging to the given policy in unregistered.


If not then use the CPU info you cpufgeq and figure out which module you need to load. This could save you money on your electric bills or battery life on a laptop. The cpb knob is never present for any processors without the underlying hardware feature e. It also may not be physically possible to maintain maximum CPU capacity for too long for thermal or power supply capacity reasons or similar. Before we start if you have a RedHat or Fedora machine you might want to try to install cpuspeed yum clufreq cpuspeed to get frequency scaling.

Using this information can be useful. Namely, it avoids changing the frequency significantly over short time intervals which may not be suitable for systems with limited power supply capacity e. That value can be used to estimate how the performance of the workload running on a CPU will change in response to frequency changes. As stated before, each of them implements a single, possibly parametrized, performance scaling algorithm.

This module might not be listed in the running modules c;ufreq is still available. Minimum time in microseconds that has to pass between two cpuufreq runs of governor computations default: If this tunable is per-policy, the following shell command sets the time represented by it to be times as high as the transition latency: