Re: [Xen-devel] more than 16 GB in a 32 Bit dom0

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2011-02-08 at 10:42 +0000, Daniel Bauer wrote:
> Hi Keir,
> 
> From: "Keir Fraser"
> > On 08/02/2011 07:27, "Daniel Bauer" <mlist@xxxxxxxxxxx> wrote:
> >> I've read in many posts, that XEN limits the 32 bit PAE kernel to 16 
> >> GB
> >> RAM, but I don't find were to enable more. Starting linux without XEN
> >> shows the whole memory. Is there still no solution?
> >>
> >> I don't have the possibility to upgrade the server to 64 bit.
> >
> > Then no.
> 
> maybe a silly question, but who sets this limit? IMHO xen, because a 
> "normal" bigmem kernel accepts upto 64 GB RAM. Is there really no switch 
> to increase the RAM under a 32 bit kernel?

The limitation is due to the 32 bit hypervisor, not the kernel.

In my experience a 32 bit (PAE) kernel running on a 64 bit hypervisor
works just fine with up to 32GB. In theory up to 160GB is possible in
the hypervisor<->PAE-kernel ABI but the kernel tends to run out of
lowmem in the 50-60GB range depending on your .config -- this true of
native too.

Ian.



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