[Beowulf] Problems with Dell M620 and CPU power throttling

[Joe Landman]

On 09/01/2013 11:49 PM, Christopher Samuel wrote:

> We pass through:
>
> intel_idle.max_cstate=0 processor.max_cstate=1
>
> on our SandyBridge nodes for just that reason.

Yes.  Mandatory on Sandy Bridge.  We often include cpu.idle=0 to handle 
an occasionally observed idle bug.

This is reminiscent of the "pausing" bug in Nehalem.  C state power 
transition, and suddenly the IOH/CPU loses seconds worth of clock ticks. 
  Very annoying.

> If you don't then the kernel will say "Oh, this is an Intel CPU, I
> know this!" (to paraphrase Jurassic Park) and enable every power
> saving feature it can find, regardless of what your BIOS/UEFI is set to.

:)

Power savings is great, when it works.  When it doesn't work, the 
wreckage thats left is epic.

-- 
Joseph Landman, Ph.D
Founder and CEO
Scalable Informatics, Inc.
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