Dual Xeon appears as dual-core in 6.1

thanos155 · 05-18-2006, 12:19 AM

Hi there!

Got pretty confused with this one. I'm trying to set a new server with FreeBSD 6.1 and it appears as if my processors are Dual-core ones while they're not. I have this in the dmesg.boot:

Code:

CPU: Intel(R) Xeon(TM) CPU 3.20GHz (3192.01-MHz 686-class CPU)
  Origin = "GenuineIntel"  Id = 0xf4a  Stepping = 10
  Features=0xbfebfbff<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,HTT,TM,PBE>
  Features2=0x641d<SSE3,RSVD2,MON,DS_CPL,CNTX-ID,CX16,<b14>>
  AMD Features=0x20100000<NX,LM>
  AMD Features2=0x1<LAHF>
  Logical CPUs per core: 2

Further down, in dmesg.boot again, I see:

Code:

FreeBSD/SMP: Multiprocessor System Detected: 4 CPUs
 cpu0 (BSP): APIC ID:  0
 cpu1 (AP): APIC ID:  1
 cpu2 (AP): APIC ID:  6
 cpu3 (AP): APIC ID:  7

Is this a problem in the CPUs being identified properly, is this the normal way it should appear, or is it a case of having paid for single-core and got given dual-core ( I wish :-) )

Thanks a lot,
Thanos

btmiller · 05-18-2006, 12:37 AM

Do your Xeons having hyperthreading enabled? AFAIK a hyperthreading CPU will appear as two CPU cores.

thanos155 · 05-18-2006, 08:19 AM

I think they are hyperthreading enabled indeed. Here's some more of my dmesg.boot.
I think the 'HTT' bit in the features line means they're hyperthreading enabled, no?

Code:

FreeBSD 6.1-RELEASE #0: Thu May 18 05:14:07 BST 2006
    root@poseidon.7mbit.net:/usr/obj/usr/src/sys/POSEIDON-WEB

Timecounter "i8254" frequency 1193182 Hz quality 0
CPU: Intel(R) Xeon(TM) CPU 3.20GHz (3192.01-MHz 686-class CPU)
  Origin = "GenuineIntel"  Id = 0xf4a  Stepping = 10
  Features=0xbfebfbff<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,HTT,TM,PBE>
  Features2=0x641d<SSE3,RSVD2,MON,DS_CPL,CNTX-ID,CX16,<b14>>
  AMD Features=0x20100000<NX,LM>
  AMD Features2=0x1<LAHF>
  Logical CPUs per core: 2
real memory  = 3220963328 (3071 MB)
avail memory = 3151065088 (3005 MB)
ACPI APIC Table: <DELL   PE1800  >
FreeBSD/SMP: Multiprocessor System Detected: 4 CPUs
 cpu0 (BSP): APIC ID:  0
 cpu1 (AP): APIC ID:  1
 cpu2 (AP): APIC ID:  6
 cpu3 (AP): APIC ID:  7

Thanks a lot!

btmiller · 05-18-2006, 11:14 PM

I'm not sure about the HTT, but I don't think there are any 3.2 GHz Xeon models that don't have hyperthreading, so this sounds like what it is.

thanos155 · 05-19-2006, 12:00 PM

Thanks for your time btmiller.

I've looked around a wee bit more and found out that it's actually better to disable hyperthreading. You can do this from the BIOS.

Just posting this for anyone that probably had similar probs.

Have a look here.

http://www.bsdforums.org/forums/show...HyperThreading

http://www.bsdforums.org/forums/show...HyperThreading

http://www.bsdforums.org/forums/show...HyperThreading

You will basically find out that you generally get better performance with HyperThreading disabled....

Thanks again..