CPU cores are not detected

[chiuyan]

I have a i7-930 system. Fedora 15 won't detect all cores. I only see 4 cores instead of 8. HT is enabled and other OS is seeing them correctly.

This seems a Fedora issue, but I don't know where to make the change. Please advice. Thank you!

[marko]

Can you post what this command shows?

lscpu

[chiuyan]

Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit
Byte Order: Little Endian
CPU(s): 4
On-line CPU(s) list: 0-3
Thread(s) per core: 1
Core(s) per socket: 4
CPU socket(s): 1
NUMA node(s): 1
Vendor ID: GenuineIntel
CPU family: 6
Model: 26
Stepping: 5
CPU MHz: 2807.039
BogoMIPS: 5501.73
Virtualization: VT-x
L1d cache: 32K
L1i cache: 32K
L2 cache: 256K
L3 cache: 8192K
NUMA node0 CPU(s): 0-3

[marko]

That's weird, so you have HT turned on in the Bios since windows sees the hyperthreading?

Have you confirmed that in the BIOS?

[PabloTwo]

Funny, Intel says your i7-930 is a 4 core CPU. Check the specs here.

[marko]

Originally Posted by PabloTwo

Funny, Intel says your i7-930 is a 4 core CPU. Check the specs here.

No, he's right, there are 4 cores but notice the Intel spec sheet just below the "# of Cores 4" also says:

# of Threads 8

Four cores with 8 threads means 2 threads per core -> hence a Hyperthreaded cpu

Under Linux, the hyperthreads show as cores, I suppose you could claim they're not really but "top", /proc/cpuinfo, and the kernel consider them as cores

[PabloTwo]

OK... I'll just slip back under my rock here.

[RHamel]

What does this show?

dmesg | grep -i cpu | grep 'Intel(R) Core(TM)'

[chiuyan]

This is what rescue system is showing on the same server. Cores are identified correctly.

Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit
CPU(s): 8
Thread(s) per core: 2
Core(s) per socket: 4
CPU socket(s): 1
Vendor ID: GenuineIntel
CPU family: 6
Model: 26
Stepping: 5
CPU MHz: 1600.000
Virtualization: VT-x
L1d cache: 32K
L1i cache: 32K
L2 cache: 256K
L3 cache: 8192K


I suppose a package is missing? I have upgraded to Fedora 16, but I still have the problem.



This is what
dmesg | grep -i cpu | grep 'Intel(R) Core(TM)' is showing

[ 0.030815] CPU0: Intel(R) Core(TM) i7 CPU 930 @ 2.80GHz stepping 05

[Adunaic]

When you say it is not seeing them, how are you "viewing" them?

[chiuyan]

Originally Posted by Adunaic

When you say it is not seeing them, how are you "viewing" them?

With rescue system (from datacenter) I see them correctly, booting the same server with Fedora will not show them.
/proc/cpuinfo only shows 4 cores.

---------- Post added at 09:17 PM ---------- Previous post was at 04:34 PM ----------

I tried a minimal CentOS 6 install and cores are identified correctly then a Fedora minimal install and problem comes again. I don't understand why.

[stevea]

The identification of cores and hyperthreading happens in the kernel - there is no extra package that controls this.
Yes it appears that *some* fedora kernel has a problem, and likely the corresponding kernel.org kernel.

So the question is - which Fedora kernel are you running ? Please post
uname -a

[chiuyan]

Hmm, I found this setting added to kernel acpi=off and deleted it. Now cores are displayed, but I see few errors in messages. It's strange as this is a new and not modified minimal installation. I'll keep you updated.

---------- Post added at 11:22 PM ---------- Previous post was at 10:05 PM ----------

So far, everything seems ok. I don't understand why acpi=off was automatically added to the kernel set up.