[CentOS] CentOS 6 : Tip for significantly increasing battery life / reducing power consumption (Thinkpad X220 Tablet)

Hello,

I was not happy with the power consumption of CentOS 6 x86_64 on a new
Lenovo Thinkpad x220 Tablet and I worked on reducing it. I just wanted
to share with the list one of the changes which gave me the most
significant improvement.

As per http://www.williambrownstreet.net/blog/?p=387, add the
following kernel arguments to the GRUB boot configuration:

pcie_aspm=force i915.i915_enable_rc6=1 i915.lvds_downclock=1
i915.i915_enable_fbc=1

(in /boot/efi/EFI/redhat/grub.conf since I use EFI,
/boot/grub/grub.conf otherwise)

As measured using PowerTop, this made the power consumption decrease
from 20W to 11W !
(I had already decreased it from 25W to 20W with the usual tips of
disabling hardware, shutting down services, switching tuned profiles,
etc.)

All in all, battery time was more than multiplied by two, and the
computer is now much more silent since the fan is not always running
like mad in order to cool the processor. The bottom of the laptop is
not anymore hot as hell.

I don't know whether this would have an impact on other hardware, but
it may be worth looking at it (even on servers?), since the above link
points to descriptions of a regression in the kernel which seems more
general.

As a side note, the Power Management Guide of Red Hat is a good
resource (analysis tools + tuned profiles):
http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html-single/Power_Management_Guide/

Cheers,

Mathieu

PS: Do you think I should book a bug in the upstream bug tracker?