CPU freqency indicator issues with kernel 3.12.X

[ryanvade]

Hello everyone,

So, with the new kernel I decided to build one. I ALWAYS build a new kernel.

Anyway, for an experiment I chose to use the Arch Linux kernel configuration for my build (Oz Unity Diamond II-B KDE built on Ubuntu 13.04).

Now for some background information. Starting with 3.12.0 the kernel is using a different Power State "controller" for Intel CPUS. This new addition to the kernel is designed for the new CPU lines (like Haswell and Broadwell). While this new PState system is supposed to increase battery life, manually configuring the CPU settings (CPU scaling, CPU frequency, other power settings) becomes almost impossible.

For the 3.12.0 kernel you can use

intel_pstate=disable

in the kernel boot parameters in GRUB to disable the new PState "controller".

For some reason this is not working correctly with 3.12.2. I am able to manually set the CPU frequncy, but two of my favorite CPU scallers (Conservative and Balance) are missing. If I remove the kernel paramater, I cannot change the CPU frequency.

Anyone have any ideas? Read anything about this?

What about our local kernel king? @DevynCJohnson

Thanks for any thoughts.

*PS. I am downloading 3.12.3 as I type.
** I wonder if this is what would be best to look at?
https://www.kernel.org/doc/Documentation/thermal/intel_powerclamp.txt

 

[DevynCJohnson]

I love kernel questions and I love my new title "Kernel King". Thanks Ryan!

The first detail that gets my attention is the fact that kernel 3.12.x is the most recent (https://www.kernel.org/), so you may have found a bug.

Second, I do not think v3.12.0 is a vanilla kernel. Kernel.org lacks a changelog for such a version (https://www.kernel.org/pub/linux/kernel/v3.x/ChangeLog-3.12.0), so the developer that custom made v3.12.0 may not have enabled a feature/driver that is needed by the CPU scalers that you want. Also, I do not see it here for download (ftp://ftp.kernel.org/pub/linux/kernel/v3.x/). Google appears to show v3.12.0 for Ubuntu and Arch, so this must be a non-vanilla kernel for Ubuntu and Arch.

I thought this new Intel CPU power driver was added in kernel 3.9.x?.

After some thought and searching, I came to this answer. This new driver can be influenced, but users cannot control the scaling (https://wiki.archlinux.org/index.php/CPU_Frequency_Scaling#CPU_frequency_driver).

 

[ryanvade]

Thanks.

3.12.0 was on kernel.org for a time. Not sure why the changelog is missing. I always get my kernels there. The Intel power driver was added with 3.9.x yes, but it was updated with 3.12.x. This updated version appears to have the cpu frequency scaling control disabled...which is why I can't get more fine control. But I am not sure why the other two CPU scaling settings are missing.

In all honesty this new powerstate setup is using more batter life then when I controlled everything with the indicator.

 

[lobo]

There is no "3.12.0", you're referring to "3.12" - this is a release, not a patch, thus no changelog.

 

[ryanvade]

There is no "3.12.0", you're referring to "3.12" - this is a release, not a patch, thus no changelog.

When it is built, the version is 3.12.0.. but yeah it is 3.12 on kernel.org. At one time it was referred to as 3.12.0, at least when it was on the front page.

And yes, it is a release not a patch. I never work with changelogs so I never look..