[ale] SMP kernel on uniprocesser

[James Sumners]

An HT enabled processor will show up as two CPUs when HT is enabled.
To take advantage of this you will need to use an SMP kernel. If you
run an SMP kernel on a machine that has a single, non-HT, CPU then the
kernel will fall back to single mode.

I have heard that HT can cause serious problems under certain
conditions. This may be why you are seeing it turned off on one of
your machines.

>From a machine of mine that has two HT Xeons:

jsumners at rockbiter:~> cat /proc/cpuinfo
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 15
model           : 2
model name      : Intel(R) Xeon(TM) MP CPU 2.00GHz
stepping        : 5
cpu MHz         : 2000.932
cache size      : 512 KB
physical id     : 2
siblings        : 2
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 2
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe cid
bogomips        : 3940.35

processor       : 1
vendor_id       : GenuineIntel
cpu family      : 15
model           : 2
model name      : Intel(R) Xeon(TM) MP CPU 2.00GHz
stepping        : 5
cpu MHz         : 2000.932
cache size      : 512 KB
physical id     : 2
siblings        : 2
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 2
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe cid
bogomips        : 3997.69

processor       : 2
vendor_id       : GenuineIntel
cpu family      : 15
model           : 2
model name      : Intel(R) Xeon(TM) MP CPU 2.00GHz
stepping        : 5
cpu MHz         : 2000.932
cache size      : 512 KB
physical id     : 3
siblings        : 2
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 2
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe cid
bogomips        : 3989.50

processor       : 3
vendor_id       : GenuineIntel
cpu family      : 15
model           : 2
model name      : Intel(R) Xeon(TM) MP CPU 2.00GHz
stepping        : 5
cpu MHz         : 2000.932
cache size      : 512 KB
physical id     : 3
siblings        : 2
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 2
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe cid
bogomips        : 3989.50

On 7/21/06, Dow_Hurst <dhurst at mindspring.com> wrote:
> If hyperthreading is turned on, you have a HT enabled processor (P4 model 631), and a smp kernel installed, you should see two CPUs in /proc/cpuinfo, via top, and in the ps aux output, correct?  Also, what is the effect of running a smp kernel on a uniprocessor machine?  I've found a very stable machine actually has a smp kernel running but Hyperthreading was turned off.  Also, I've got a new machine that is not stable yet and is the situation I first stated above.  I'm now running it with a default kernel and hyperthreading turned off.
> Thanks,
> Dow
>
>
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-- 
James Sumners
http://james.roomfullofmirrors.com/

"All governments suffer a recurring problem: Power attracts
pathological personalities. It is not that power corrupts but that it
is magnetic to the corruptible. Such people have a tendency to become
drunk on violence, a condition to which they are quickly addicted."

Missionaria Protectiva, Text QIV (decto)
CH:D 59