Missing CPU threads??

Franz Hopper · 2011-02-21 04:01:09

For the last few days I have been setting up my Arch Linux 2010.05 install and have been very happy with it. But theirs one thing that google, the wiki and the forums cant seem to answer for me. I'm running a rig with an EVGA Super-Record 2 mobo coupled with a Intel Xeon E5620 which has 4 cores and 8 threads. In Windows 7 and Ubuntu 10.10 it see's all 8 threads. But Arch is only seeing 4 threads?

Here is /etc/cpuinfo: http://pastebin.com/ZdTKmpmn
And here's dmesg: http://pastebin.com/uJ3iXPa8

Any help would be appreciated, I just cant figure out why this is happening.

karol · 2011-02-21 08:59:00

What does'

Booting paravirtualized kernel on bare hardware

mean?

falconindy · 2011-02-21 14:35:19

karol wrote:

What does'

Booting paravirtualized kernel on bare hardware

mean?

That appears in everyone's dmesg.

I'm dubious that it's related, but is there a specific problem that you're solving by disabling acpi?

tom5760 · 2011-02-21 17:30:15

What do you mean by "threads"? A thread is something that programs use, it has nothing to do with your processor. If your processor is quad-core, then you will see four entries in /etc/cpuinfo (which you do). Are you sure there is actually a problem?

anonymous_user · 2011-02-21 17:32:54

He means his processor has Hyper-threading so although its a quad-core, it can execute 8 threads.

Last edited by anonymous_user (2011-02-21 17:33:25)

Franz Hopper · 2011-02-21 17:41:02

Sorry, I forgot to mention about ACPI. This board locks up both the live-CD and an install if ACPI is on. The live-CD would lock up at random points and If using an already installed system it would hang with a blinking cursor. So I played around and found that ACPI was the cause. I dont belive it could be related to this could it? I plan to use this box for MPICH2 for a class I'm teaching and would like to get all the power out of this proc as I can.

Last edited by Franz Hopper (2011-02-21 17:49:55)

falconindy · 2011-02-21 20:56:32

It'd be interesting to compare a dmesg log from ubuntu. Is the Ubuntu install 64 bit as well?

tom5760 wrote:

What do you mean by "threads"? A thread is something that programs use, it has nothing to do with your processor. If your processor is quad-core, then you will see four entries in /etc/cpuinfo (which you do). Are you sure there is actually a problem?

http://ark.intel.com/Product.aspx?id=47925 - note how intel designates cores and threads. My i7 980x shows CPUs 0-11 in /proc/cpuinfo despite there only being 6 cores. Yes, the concept of a thread sometimes refers to a userspace concept of a lightweight process, but in general its shortened way of denoting threads of execution which can apply to processor cores executing multiple instructions in parallel.

R00KIE · 2011-02-21 21:24:47

Franz Hopper wrote:

So I played around and found that ACPI was the cause. I dont belive it could be related to this could it?

It might be, disabling acpi turns a few things off so that could be causing trouble. You can test that easily, disable acpi on ubuntu and check if the 8 logical cores show up or if you can see only 4.

Franz Hopper · 2011-02-21 21:27:04

Well this is interesting, It would seem I made a mistake. Ubuntu 9.10 & 10.10 x32 & x64 only see 4 CPU's as well. I could have sworn that they recognized them all but I must have been thinking of one of the clusters Sun boxes I was working on. So the end result now is Windows 7 Pro x64 see's all 8 and both Arch & Ubuntu on both archs dont see all 8.

Edit: Ubuntu needs ACPI off as well to function.

Last edited by Franz Hopper (2011-02-21 21:29:44)

dburden · 2011-03-02 17:54:49

I believe that turning off ACPI disables Hyperthreading.

Consider a finer grained option:

https://wiki.ubuntu.com/DebuggingACPI

graysky · 2011-03-02 21:06:53

@op - have you tried installing and using a microcode update with ACPI on? Depending on how new your mobo is, the BIOS might not yet have the updated microcode for the CPU.

Arch Linux

#1 2011-02-21 04:01:09

Missing CPU threads??

#2 2011-02-21 08:59:00

Re: Missing CPU threads??

#3 2011-02-21 14:35:19

Re: Missing CPU threads??

#4 2011-02-21 17:30:15

Re: Missing CPU threads??

#5 2011-02-21 17:32:54

Re: Missing CPU threads??

#6 2011-02-21 17:41:02

Re: Missing CPU threads??

#7 2011-02-21 20:56:32

Re: Missing CPU threads??

#8 2011-02-21 21:24:47

Re: Missing CPU threads??

#9 2011-02-21 21:27:04

Re: Missing CPU threads??

#10 2011-03-02 17:54:49

Re: Missing CPU threads??

#11 2011-03-02 21:06:53

Re: Missing CPU threads??

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