[TriLUG] hyperthreading, smp, and irqbalance

[Kevin Otte]

On Tue, May 09, 2006 at 11:41:06AM -0400, Dane Miller wrote:
> I have a production file server (P4 2.8ghz w/HT), that is approaching
> its quarterly scheduled maintenance downtime.  I'm wondering if it's
> worth switching to an SMP kernel to take advantage of hyperthreading.
> 
> The box runs very happily on its current 2.6.8-3 Debian Sarge kernel.
> 
> Are there any risks to SMP on a single CPU w/HT?

There is some debate as to whether I/O takes a hit.  I'm sure others in
here could provide many technical studies one way or the other, but in my
unmeasured experience you get slower I/O with HT on.

If you do have HT turned on in the BIOS, you ought to be running an SMP
kernel.

> Any Debian-specific problems?

Nope.

> Should I use irqbalance?

If you are going to use an SMP kernel, yes.  Debian will prompt you that if
you are using it with HT, you should put it in "one-shot" mode.  It will
balance the IRQs once at startup instead of on a continuous basis.

-- 
Kevin Otte, N8VNR
nivex at nivex.net
http://www.nivex.net/

-=-

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