Fix Sandy Bridge power regression issue in 3.6-3.7 kernel

Proud owners of Intel Sandy Bridge-powered laptops have been experiencing power regression problems for three months now. Starting somewhere at 3.6.x kernel the power consumption suddenly seared high as well as the overall CPU temperature. My typical laptop temperature being around 45°C with introduction of 3.6 it rose to 80. Average battery life jumped from 3-4 hours to pathetic hour and a half. Briefly speaking the changes were too much to bear so I rolled back to 3.5.6 and stayed there for these three months.

Eventually the commit that introduced the regression was identified but neither 3.6 branch nor 3.7 hadn't got it reverted in them. Only 3.8 branch finally fixed the problem but it is still in its release candidate status, so it's a question when will it reach the general audience.

I've been for some time following this thread where Arch users shared their experiences with different kernel versions. William Giokas is a regular poster there, and he is the person who kindly builds the newest versions of the kernel for Arch Linux. Here's a README on how to install his kernels instead of building them on your own.

After I had upgraded to 3.8-rc5 from 3.5.6 I didn't notice any visible regression in power consumption and temperature. The temperature floats around 47-48 degrees and the consumption averages on 15W mark.

The process of upgrading to kernel built by William is pretty straightforward. Here it is step by step:

  • add William's repo to your pacman.conf as described in README;
  • install linux-mainline package;
  • update grub to include the new kernel in the list;
grub-mkconfig -o /boot/grub/grub.cfg
  • rebuild tlp and tp\smapi-mainline packages from AUR.

Now you can safely update all other packages that you otherwise postponed because of the kernel rollback.