** Description changed: 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: http://ubuntuforums.org/showthread.php?t=1822629 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 IPI>" Someone much more advanced than I figured out how to eliminate this - problem and recompiled the kernel (which he posted in the thread I + 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_enable_rc6=1" + significantly improves battery life (even more so with the no sparse irq + kernel...sparse irq seems to be a separate, related problem), but that + kernel parameter brings with it intermittent graphical glitches and + freezes (which are experienced with kernel 2.6.x). Hope that + info/clarification helps.
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/834037 Title: Huge power regression in kernel 3.x on Sandy Bridge laptops To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/834037/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
