Huge power regression in kernel 3.x on Sandy Bridge laptops
I would like to report what myself and several others believe to be a
serious bug affecting all Linux kernels 3.0 and up, and none below 3.0
(2.6.x and lower). I tested this using .deb kernel packages for Ubuntu 11.10.
One-sentence description: On certain hardware, the 3.x series kernels
drain a considerable amount more power than the 2.6-series kernels, up
to 40% more, even when idle.
The specific hardware I have personally tested is a Lenovo ThinkPad
X220 with an Intel SandyBridge i7 2620M processor. We think that this
bug is POSSIBLY specific to this processor, or family of processors,
commonly used in notebooks. A complete thread of mine and others'
results, evidence, and troubleshooting process is located at:
We have tried several different 3.0 and 3.1-series kernels, all with
the same problems. One part of the problem was that the following
(revealed by powertop) was causing excessive processor wakeups
compared to the 2.6-series kernels: "[Rescheduling interrupts] <kernel
Someone much more advanced than I figured out how to eliminate this
problem and recompiled the kernel with "no sparse irq," whatever that means (which he posted in the thread I
linked to previously), but power usage is still improved only
slightly, nowhere near kernel 2.6 levels.
There is a lot more information I could give you here, but all of it
is contained within the thread I linked to. If you have any specific
questions, I will answer as quickly as possible.
Note, 2011-10-10: This bug seems to have a lot to do with the graphics of these processors. Adding kernel parameter "i915.i915_
- Huge power regression from kernel 2.6.x on Sandy Bridge laptops
+ Huge power regression in kernel 3.x on Sandy Bridge laptops
|Changed in ubuntu:|
|status:||New → Confirmed|