[ale] SMP kernel on uniprocesser

[Jeff Lightner]

Right.  In recent search I found that HyperThreading was problematical
on RedHat/Fedora Core below version 4 and it's not certain its fixed
after that.

-----Original Message-----
From: ale-bounces at ale.org [mailto:ale-bounces at ale.org] On Behalf Of
To: ale at ale.org
James Sumners
Sent: Friday, July 21, 2006 4:19 PM
To: Dow_Hurst; Atlanta Linux Enthusiasts
Subject: Re: [ale] SMP kernel on uniprocesser

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
>
>
> No sig.
> _______________________________________________
> Ale mailing list
> Ale at ale.org
> http://www.ale.org/mailman/listinfo/ale
>


-- 
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
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