linux-kernel - Bug Report for Linux Kernel 3.x

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Date:	Tue, 23 Aug 2011 19:19:35 -0400
From:	Steevven1 <steevven1@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: Bug Report for Linux Kernel 3.x

Hello,

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).

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
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.

Thanks a lot for your assistance. Please confirm that you received this email.

Steven Keys!
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