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Re: Actual dom0 memory much lower than dom0_mem setting


  • To: Andy Smith <andy@xxxxxxxxxxxxxx>
  • From: Juergen Gross <jgross@xxxxxxxx>
  • Date: Fri, 10 Apr 2026 14:26:47 +0200
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  • Cc: xen-users@xxxxxxxxxxxxx
  • Delivery-date: Fri, 10 Apr 2026 12:27:05 +0000
  • List-id: Xen user discussion <xen-users.lists.xenproject.org>

On 10.04.26 14:18, Andy Smith wrote:
Hi Jürgen,

On Wed, Apr 08, 2026 at 03:26:05PM +0200, Jürgen Groß wrote:
On 03.04.26 17:23, Andy Smith wrote:
So, aiming to get a usable 8192M dom0 memory, I bumped it up by the
shortfall of 1839M:

$ sudo xl info | grep xen_commandline
xen_commandline        : placeholder dom0_mem=10031M dom0_max_vcpus=2 
com1=115200,8n1,0x2f8,10 console=com1,vga ucode=scan smt=1 no-real-mode edd=off

In case you don't need to balloon dom0 up, you can use "dom0_mem=8192,max:8192"

Ah, thanks! I used to use the max part a long time ago, I forget why I
stopped doing so. Using that has made things a bit better: now it sees
7914M. Is that expected?

Yes. The space occupied by the kernel itself and the mentioned administration
memory for RAM (struct page array) isn't included in the reported memory size.
This happens on bare metal, too.


Juergen

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