Re: CPU utilization

Julian Elischer wrote:
Robert Watson wrote:

On Thu, 12 Apr 2007, Dag-Erling Smørgrav wrote:

Randall Stewart <rrs@xxxxxxxxx> writes:
machdep.hyperthreading_allowed: 0

Note that enabling hyperthreading is more likely to harm performance than to help it. You should just disable it in the BIOS, and run a UP kernel.

Historically this has been true, but some more recent results I've seen suggest that both hyperthreading hardware has improved, and the efficiency of our SMP implementation and scheduler has lead to it being more effective used. I would reevaluate this on more modern hardware and using a more recent kernel before assuming this remains true for your application.

In addition to this, to answer the original question, I remember a commit so that if you disable a cpu (or HT cpu) it doesn't get counted
in the CPU % so if you have 2 cpus and disable one hten prior to that
commit it was not possible to get > 50% busy but after that commit
you could get 100% "of the available CPUs". That fix is not (I believe)
in 6.2.

That's correct. The fix went in after RELENG_6_2 has been branched.

-Maxim

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