[Beowulf] Good IB network performance when using 7 cores, poor performance on all 8?

[Joe Landman]

On 04/24/2014 12:17 PM, John Hearns wrote:
> I am with Joe regarding looking at the interrupts.
>
> However, could this be a difference with the power management with the
> Redhat kernel?
> ie. when running on 8 cores you are tripping over some thermal threshold
> and causing a throttle back to a lower C-state?

Yeah, that was the other thing I'd forgotten about.  Might want to tweak 
Cstates to C1.  It could be going over-power and throttling.  Turn of 
ASPM and other (fairly painful) things.



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