[CentOS] CentOS 5.4 x86_64 only detects 32GB RAM while Fedora x86_64 correctly lists 128GB

Thomas Harold thomas-lists at nybeta.com
Mon Dec 7 16:39:19 UTC 2009

On 12/7/2009 7:24 AM, Diederick Stoffers wrote:
 > [root at localhost ~]# uname -a
 > Linux localhost.localdomain 2.6.18-164.6.1.el5xen #1 SMP Tue Nov 3
 > 16:48:13 EST 2009 x86_64 x86_64 x86_64 GNU/Linux

If you dig back through the xen-users mailing list, there's a thread 
that discusses this recently.  Look for a subject of "[Xen-users] Memory 
not seen in Dom0" back around Nov 8th.  I tried to get GMane's web 
interface to toss up a direct link to the thread, but gave up.


Supposedly, it's not an issue unless you really really want >32GB in the 
Dom0 host.  The Xen 64bit kernel (currently?) limits the Dom0 to 32GB. 
But any guest VMs that you create will initially use the RAM not used by 
the Dom0.

Most folks recommend that you limit Dom0's memory usage in grub.conf 
(using the dom0_mem= argument).  Or you can set it later using "xm 
mem-set 0 ###M".

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