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?t22629

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!

On Tue, Aug 23, 2011 at 07:19:35PM -0400, Steevven1 wrote:

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?t22629

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!

Hi Steve,


You said the problem with rescheduling interrupt disappeared but you
haven't said why. After reading the thread it seems it was about
Sparse irq config beeing enabled? And that disappeared after
sparse irq got disabled?

If so that looks like a first bug.

Also now that you don't see that problem anymore but still
a problem with power consumption, what does powertop report to
you?

Thanks.

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.

On Tue, Aug 23, 2011 at 07:19:35PM -0400, Steevven1 wrote:
 > 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.

Sounds like https://bugzilla.redhat.com/show_bug.cgi?idr7579
Try booting with i915.i915_enable_rc6=1

       Dave

Thanks for the comment. I have already tried this with several
different 3-series kernels. There was no effect on power consumption
or output from powertop.

SK!


On Tue, Aug 23, 2011 at 11:58 PM, Dave Jones wrote:
> On Tue, Aug 23, 2011 at 07:19:35PM -0400, Steevven1 wrote:
>  > 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.
>
> Sounds like https://bugzilla.redhat.com/show_bug.cgi?idr7579
> Try booting with i915.i915_enable_rc6=1
>
>        Dave
>
>
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