bug 2 cpus shows as 4 cpus

bug 2 cpus shows as 4 cpus

[Jeff Chua]

I'm running 2.4.20-pre9 on DELL server with Xeon dual processors, but
/proc/cpuinfo shows not 2, but "4" cpus!

The bogomips semms to indicate 2 cpus. (3971.48 is about 2GHz x 2).

Is this problem related to Xeon? I've other SMP boxes with P3, but they
reports correctly 2 cpus.

thanks,
Jeff.




Here's the last cpu ...

processor       : 3
vendor_id       : GenuineIntel
cpu family      : 15
model           : 2
model name      : Intel(R) XEON(TM) CPU 2.00GHz
stepping        : 4
cpu MHz         : 1988.912
cache size      : 512 KB
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
bogomips        : 3971.48

Re: bug 2 cpus shows as 4 cpus

[Dave Jones]

On Wed, Oct 09, 2002 at 07:39:37AM +0800, Jeff Chua wrote:
 > 
 > I'm running 2.4.20-pre9 on DELL server with Xeon dual processors, but
 > /proc/cpuinfo shows not 2, but "4" cpus!
 > The bogomips semms to indicate 2 cpus. (3971.48 is about 2GHz x 2).
 > Is this problem related to Xeon? I've other SMP boxes with P3, but they
 > reports correctly 2 cpus.

P4 xeon has hyperthreading.

-- 
| Dave Jones.        http://www.codemonkey.org.uk

Re: bug 2 cpus shows as 4 cpus

[Robert Love]

On Tue, 2002-10-08 at 19:39, Jeff Chua wrote:

> I'm running 2.4.20-pre9 on DELL server with Xeon dual processors, but
> /proc/cpuinfo shows not 2, but "4" cpus!
> 
> The bogomips semms to indicate 2 cpus. (3971.48 is about 2GHz x 2).
> 
> Is this problem related to Xeon? I've other SMP boxes with P3, but they
> reports correctly 2 cpus.

Hahaha, dude, you have hyper-threading!  Each of your Xeons has two
logical processors that share most processor resources but implement two
independent pipelines.  So you have four schedulable processors in
total.

Google around for hyper-threading, HT, and SMT.  It is in all P4-class
Xeons and soon all regular P4s.

	Robert Love

Re: bug 2 cpus shows as 4 cpus

[David S. Miller]

   From: Jeff Chua <jchua@fedex.com>
   Date: Wed, 9 Oct 2002 07:39:37 +0800 (SGT)

   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

Flag "ht" HyperThreading is set, that is why it looks like
4 processors instead of two.