CPU utilization

Robert Watson rwatson at FreeBSD.org
Thu Apr 12 14:40:51 UTC 2007

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

> Randall Stewart <rrs at cisco.com> 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.

Robert N M Watson
Computer Laboratory
University of Cambridge

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