Re: Dual P4 2.4Ghz Xeon With Hyperthreading enabled...

From: John Baldwin <jhb_at_FreeBSD.org>
Date: Wed, 13 Aug 2003 12:52:14 -0400 (EDT)
On 13-Aug-2003 Dr. Richard E. Hawkins wrote:
> On Wed, Aug 13, 2003 at 11:35:14AM -0400, John Baldwin wrote:
> 
>> On 13-Aug-2003 Dr. Richard E. Hawkins wrote:
>> > On Tue, Aug 12, 2003 at 08:33:57PM -0500, Cagle, John (ISS-Houston) wrote:
>> >> I think the valid settings are only 0 or 1, with the default being 1
>> >> which will disable all logical CPUs.  If you want to enable the extra
>> >> logical CPUS, then set it to 0 (zero).  They will come online
>> >> immediately.
> 
>> > That can't be right.  I've never done anything to configure the logical
>> > cpus on mine; they just showed up unexpectedly when i switched from
>> > stable to current.  Now I have:
> 
>> > slytherin ttyp1:hawk>sysctl -a |  grep cpu
>> > kern.threads.virtual_cpu: 4
>> > kern.ccpu: 1948
>> > kern.smp.cpus: 4
>> > hw.ncpu: 4
>> > machdep.cpu_idle_hlt: 1
>> > machdep.hlt_cpus: 10
>> > machdep.hlt_logical_cpus: 1
>> > machdep.logical_cpus_mask: 10
> 
>> > It launches four logical cpus all on it's own.  It did panic during
>> > shutdown yesterday; If I read the messages right as it flashed by, it
>> > was because cpu#2 got the shutdown order.
> 
>> Your logical CPU's aren't doing anything though, even though they are
>> started up.  John's explanation is correct.
> 
> I've also got the report in dmesg,
> 
> SMP: AP CPU #1 Launched!
> SMP: AP CPU #2 Launched!
> SMP: AP CPU #3 Launched!
> 
> 
> Doesn't this mean that they *are* active?

No, it means the kernel has started them up.  CPU's whose bits are set
in machdep.hlt_cpus don't execute any user tasks.  Instead, they just
sit in a loop executing the 'hlt' instruction doing nothing but servicing
interrupts.

-- 

John Baldwin <jhb_at_FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/
Received on Wed Aug 13 2003 - 07:52:15 UTC

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