Improving power consumption on Ubuntu laptop with ‘Sandy Bridge’ processor

*Tested on: Lenovo ThinkPad T520 with Ubuntu 10.04 LTS (Lucid Lynx) and backported kernel 3.0.0-13

Recently I found interesting articles about increased power consumption on Sandy Bridge processors with new generations of Linux kernels.

According to article http://www.phoronix.com/scan.php?page=article&item=intel_i915_power&num=1 there is a solution for this issue.

So, with a help of uncle Google and this article: http://www.techytalk.info/linux-kernel-2-6-38-2-6-39-power-regression-workaround/#more-1972 I finally managed to test it. I was honestly surprised by result, since at beginning I was quite sceptic, primarily because I’m not experienced Linux user and I had reasonable doubts about my ability to do something like this. 🙂

I tested it step by step, and I done lot’s of measuring and rebooting, but I’ll describe only final steps.

a) I tried some tools for observing/monitoring, but at the end I liked and used these two: powertop and dstat. They are both in repository, so installing is simple:

sudo apt-get install powertop dstat

Using of powertop is simple. Just issue a command:

powertop

For dstat there are some parameters that u can find in man or issuing dstat –help. I used this command:

dstat --time --power --battery --battery-remain 10

Laptop was running on battery only, and before I changed anything I measured its power consumption in a conditions that I’ll test every time I change something in grub conf file.
Initial power usage was ~20W.

1. Open GRUB configuration file:

gksudo gedit /etc/default/grub

2. Find the GRUB_CMDLINE_LINUX_DEFAULT line
(usually looks like this: GRUB_CMDLINE_LINUX_DEFAULT=”quiet splash”)

3. Change that line into

GRUB_CMDLINE_LINUX_DEFAULT=”quiet splash pcie_aspm=force pcie_aspm=force i915.i915_enable_rc6=1 i915.i915_enable_fbc=1 i915.lvds_downclock=1″

(details about every option can be found on mentioned link)

4. run command to update GRUB configuration:

sudo update-grub

5. restart computer

——–
In my case I had final power consumption of ~12W in the same conditions as I started observing/measuring. Comparing it to initial ~20W I found it as quite successful venture. 🙂
——–

The next thing I decided to fix was Bluetooth. Damn thing was turned on every time I reboot computer, no mater I was keep turning it off. >:[

Thanks to https://bugs.launchpad.net/ubuntu/+source/bluez/+bug/381913, I finally managed to turn it off on startup:

I created file .profile in my home folder and I put this command there:

rfkill block bluetooth

That fixed problem with untamed Bluetooth, and it additionally improved power consumption.

Related articles

• Installing Ubuntu 10.04 LTS (Lucid Lynx) on Lenovo ThinkPad T520 (putokaz.wordpress.com)
• Kernel Bug Means Linux Power Usage Remains High (linux.slashdot.org)