Hyperthreading question

[Dwayne MacKinnon]

Hi all,
I'm upgrading some machines from 4.8-RELEASE to 4.10-RELEASE. The 
machines in question are dual-processor xeon boxes. Now, my boss is 
adamant in that he doesn't want hyperthreading enabled on the machines.

In 4.8-RELEASE things were simple... I just didn't add the options HTT 
line to my kernel config file. In 4.10-RELEASE though, HTT is enabled by
default.

So, is there any way to shut off the hyperthreading? I've tried 
disabling it in the BIOS, and had no luck whatsoever.

Thanks,
DMK
PS: A direct reply would be welcome. I'm not subscribed to the mailing list.
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Re: Hyperthreading question

[Eugene Lee]

On Tue, Jun 08, 2004 at 03:36:28PM -0400, Dwayne MacKinnon wrote:
: 
: I'm upgrading some machines from 4.8-RELEASE to 4.10-RELEASE. The 
: machines in question are dual-processor xeon boxes. Now, my boss is 
: adamant in that he doesn't want hyperthreading enabled on the machines.
: 
: In 4.8-RELEASE things were simple... I just didn't add the options HTT 
: line to my kernel config file. In 4.10-RELEASE though, HTT is enabled by
: default.
: 
: So, is there any way to shut off the hyperthreading? I've tried 
: disabling it in the BIOS, and had no luck whatsoever.

Hyperthreading is built into the kernel by default starting with
FreeBSD-4.9.  However, it is not enabled by default.  To do so,
do a sysctl machdep.hlt_logical_cpus=0

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