Re: [Xen-users] Accessing new extra memory

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> 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?

Daniel says not, so I'll defer to his superior knowledge.

In general, you could run "xm info" and see if you support x86_32p guests in 
the xen_caps field.  If you don't, then you don't have PAE support.

> > 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?

If you want to support the extra memory, then definitely you'll need to 
upgrade to a PAE release (or 64-bit if that's available), either from source 
or from the RPMs (or conceivably by upgrading to RHEL5, which isn't based on 
3.1 but does support PAE).

I don't know how up-to-date the XenSource RPMs are kept.

Supporting PAE should allow the default fedora Xen kernels to run on your 
system easily too.

Cheers,
Mark

> 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



-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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