Dual processor but see Quad processor

[Pedro Fernandes Macedo]

Yeak,

The 4 processors are ok. The latest Xeon and Pentium 4 processors have a 
technology called Hyperthreading . Using it , each processor works to 
the OS as being two logical processors... This explains the 2 "extra" 
processors you see...
To disable this , you have to disable Hyperthreading in the bios or 
disabling ACPI in the kernel... ( I found out that ACPI has to be 
enabled to make the kernel recognize the virtual CPU when compiling a 
kernel to a Xeon machine we bought recently). Some tests show this 
should be disabled in linux , because this leads to some performance 
penalties , but I'm leaving it enabled anyway...

Pedro Macedo

Message: 29
To: fedora-list at redhat.com
From: Yeak Nai Siew <yeak at md.com.my>
Subject: Dual processor but see Quad processor
Date: Fri, 5 Dec 2003 09:53:06 +0800
Reply-To: fedora-list at redhat.com


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Hi all,

I installed Fedora Core 1 on IBM eServer with the following spec:
- 1U
- 2 x 36 GB Hardware RAID 1 (LSI and driver used is mpt)
- 2 x 2.8 Ghz Xeon
- 4 x 1 GB RAM

Right after install and logged in, the Gnome desktop seems unstable.
Clicking the menu will occasionally paused for 1 or 2 seconds. I left
it idle and not touching it, but it crashed automatically. Message log
shows gdm-binary having problem. Not sure if it is so.

Then I run "top" and I notice it shows 4 CPU. I know this server only
have 2. None of this 4 CPU shows any status. Idle is "0%". The status
is wrong.

Then I tried RHEL AS 3, looks more stable, but the "top" also show 4
CPU. This time it shows the figure. Idle is around 98% to 100%. But the
status run across all the 4 CPU (the physical CPU is only 2...)

Why seeing 4, not 2? Is there a way to pass kernel parameter during
bootup to force it to use 2 only?

Thanks.


-- Yeak Nai Siew << Mac OS Forever >> << Linux Forever>> >>> 
http://www.redhat.com/rhce/rhce806200928901893.html <<<