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Re: [Xen-users] Accessing new extra memory

On Wed, 27 Jun 2007, Mark Williamson wrote:

You need to be running a PAE release of Xen to use more than 4Gig of memory.

How do you tell if PAE is enabled or not? Was there any PAE in Xen 3.0.2 at all?

I'm guessing you're not, right?  I'm afraid that means upgrading both your
Xen and you dom0 / domU kernels, which I realise is a pain.

The RPMs of Xen 3.1 may provide what you need (plus an upgrade to the latest
stable release of Xen).  They're compiled for PAE and are specifically for
RHEL 4.5 although they're not officially supported by anyone...

We'll be going there eventually, maybe we should just bite the bullet
and do it now?

Steve Timm



The RedHat RHEL 4.5 upgrade includes a domU kernel which will also be PAE, so
upgrading Xen to PAE will enable you to use the official RH kernels in the
domUs.

Cheers,
Mark

On Wednesday 27 June 2007, Steven Timm wrote:
Hi--I am currently running i386 version of xen 3.0.2
[root@fermigrid0 ~]# uname -a
Linux fermigrid0.fnal.gov 2.6.16-xen3_86.1_rhel4.1 #1 SMP Thu Apr 13
06:52:14 PDT 2006 i686 i686 i386 GNU/Linux


The machine previously had 4GB of RAM, and was booted
with option dom0_mem=1024000 to ensure at least 1GB of RAM in
dom0. I am also running five Xen instances using 500MB of RAM apiece.

Today I upgraded the RAM to 12GB.  I attempted to leave dom0 at 1GB
and increase each of the Xen instances to 1GB for starters.
What actually happened is by the time I tried to start the
third 1GB instance I ran out of memory, it said there were only
168MB available.

Is there something in this kernel that limits us to only 4GB of RAM?
If so, what is the way around it? I can upgrade if necessary.
(For that matter even before this, the sum of dom0 plus the 5 xen
instances didn't add up to the total amount of memory in the machine.)

[root@fermigrid0 ~]# xm list
Name                              ID Mem(MiB) VCPUs State  Time(s)
Domain-0                           0      538     4 r-----  2694.1
fermigrid0-xen1                    5      500     2 -b----  1107.0
fermigrid0-xen2                    6      500     2 -b----    41.2
fermigrid0-xen3                    7      500     2 -b----    86.2
fermigrid0-xen4                    8      500     2 -b----    41.3
fermigrid0-xen5                    9      500     2 r-----    42.1



Steve





--
------------------------------------------------------------------
Steven C. Timm, Ph.D  (630) 840-8525
timm@xxxxxxxx  http://home.fnal.gov/~timm/
Fermilab Computing Division, Scientific Computing Facilities,
Grid Facilities Department, FermiGrid Services Group, Assistant Group Leader.

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