RE: [Xen-users] System-RAM: 3325MB question

["Petersson, Mats" <Mats.Petersson@xxxxxxx>]

> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of 
> Frank Schubert
> Sent: 28 April 2006 09:47
> To: xen-users Mailinglist
> Subject: [Xen-users] System-RAM: 3325MB question
> 
> Hi,
> 
> first I want to send many thanks to the Xen developers and to 
> this list.
> 
> Here's my question:
> Today i upgraded a server to 4GB RAM but Xen only shows 3325MB RAM?:
> 
>  Xen version 3.0.2-2 (xenod@xxxxxxxxxxxx) (gcc version 3.3.3 
> 20040412 (Red Hat Linux 3.3.3-7)) Thu Apr 13 17:34:06 BST 
> 2006  Latest ChangeSet: Thu Apr 13 15:18:37 2006 +0100 
> 9617:5802713c159b
> 
> 
> Do i already need PAE extension for this?
> (I thought PAE is only needed if i want more than 4GB.)

Short answer: Yes.

The reason you only see 3.3GB is that the PCI space has to live
somewhere - and for practical purposes, the BIOS deciedes that SOMEWHERE
is below 4GB - so you get your PCI devices taking up around 700MB, and
that is what eats up the memory. 

The RAM will then be "redirected" to above 4GB - so you need PAE or
64-bit addressing (which is PAE with a fourth level of page-tables
added) to see more than 4GB of address space, and since some of your ram
is above 4GB, you need PAE on. 

--
Mats

> 
> Thank you in advance,
> Frank Schubert
> 
> --
> Frank Schubert
> Systemadministration
> EsPresto AG
> Breite Str. 30-31
> 10178 Berlin/Germany
> Tel: +49.(0)30.90 226.750
> Fax: +49.(0)30.90 226.760
> f.schubert@xxxxxxxxxxxx
> 
> _______________________________________________
> Xen-users mailing list
> Xen-users@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-users
> 
> 


_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users