[Beowulf] Problems with Dell M620 and CPU power throttling

Joe Landman landman at scalableinformatics.com
Sun Sep 1 21:02:10 PDT 2013

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.
email: landman at scalableinformatics.com
web  : http://scalableinformatics.com
phone: +1 734 786 8423 x121
fax  : +1 866 888 3112
cell : +1 734 612 4615

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