enable smp / hyperthreading

Robert Marella rmarella at gmail.com
Tue Nov 8 01:25:25 GMT 2005


On Mon, 7 Nov 2005 11:16:19 -1000
Robert Marella <rmarella at gmail.com> wrote:

> On Mon, 7 Nov 2005 20:05:24 +0100
> Roland Smith <rsmith at xs4all.nl> wrote:
> 
> > On Mon, Nov 07, 2005 at 07:53:20PM +0100, jwl at io.dk wrote:
> > > Hi
> > > 
> > > I've just installed 6.0-RELASE and am trying to get SMP to work (I
> > > have af Pentium 4 with HT). So I've compiled the kernel with
> > > 'options SMP' and according to dmesg the two CPUs are found:
> > > 
> > > FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs
> > >  cpu0 (BSP): APIC ID:  0
> > >  cpu1 (AP): APIC ID:  1
> > > 
> > > But I'm not sure that both are enabled, because at this is at the
> > > end of dmesg and I dont see the other CPU being enabled somewhere:
> > > 
> > > SMP: AP CPU #1 Launched!
> > 
> > I think it is referring to the Auxiliary Processor (AP), because the
> > BSP (don't know what that stands for, though) is obviously already
> > active. 
> > > According to 'sysctl -a' there are 2 CPUs, but only 1 active and
> > > SMP doesnt seem to be disabled:
> > > 
> > > kern.smp.cpus: 2
> > > kern.smp.disabled: 0
> > > kern.smp.active: 1
> > 
> >   sysctl -d kern.smp.active
> >   kern.smp.active: Number of Auxillary Processors (APs) that were
> >   successfully started
> > 
> > This is the number of _extra_ CPUs, which chould be 1.
> >  
> > Roland
> 
> If hyperthreading is working the ouput of 'top' should have a C column
> and will show either a 0 or a 1.
> 
> AFAIK HTT is still disabled because of a security risk. See:
> 
> ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-05:09.htt.asc
> 
> If you do not believe you are at risk, there is a work around included
> in the above site.
> 
> YMMV. I have been known to be wrong before. :-)
> 
> Robert
>

Replying to myself. It seems that once again I am wrong. 

I commented out the  machdep.hyperthreading_allowed=1
in /boot/loader.conf on my 6.0 system and I still have the C column and
showing 2 processors.

Sorry about the noise.

Robert


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