Re: [Xen-users] Accessing new extra memory

[Steven Timm <timm@xxxxxxxx>]

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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