only one logical CPU used in Xeon

John Baldwin jhb at
Wed Mar 11 06:55:35 PDT 2009

On Wednesday 11 March 2009 6:21:50 am Robert Heron wrote:
> > Are you 100% sure that your processor are really multi-core
> > and not just hyperthreaded?  Please post the relevant lines
> > from /var/run/dmesg.boot or output from the `dmesg` command
> > (as Adrian already suggested), preferably on a recent
> > FreeBSD system (i.e. 7.1).  The top 25 lines should be
> > sufficient.
> I have tried 6.2, 6.4 and 7.1 on two different servers. The first  
> server of them (older) is Intel SE7501HG2 + 2 x Xeon 2.44GHz (2 cores  
> in each Xeon)
> The second one (newer) is Intel S5000VSA + 2 x Xeon 2.66GHz (4 cores  
> in each Xeon)

The older box does have hyperthreading and the new one does not, so 6.x is 
working properly.  The issue with 7.1 is that if you use the default 
scheduler (ULE) it doesn't actually honor the hyperthreading_allowed 
variable.  7.x after 7.1 has been changed to at least honor it as a tunable 
in the ULE case (though the sysctl doesn't work).  If you use 4BSD on 7.1 
then the tunable and sysctl will work fine.

John Baldwin

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