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RE: [Xen-users] dom0 incorrect mem size

  • To: Pasi Kärkkäinen <pasik@xxxxxx>
  • From: "Robbie Garertt" <rgarrett@xxxxxxxxxxxxxx>
  • Date: Fri, 12 Mar 2010 19:29:22 -0500
  • Cc: xen-users@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Fri, 12 Mar 2010 16:35:10 -0800
  • List-id: Xen user discussion <xen-users.lists.xensource.com>
  • Thread-index: AcrBxwvk1lqw+WZqSKmlu3sox164xQAfS4YE
  • Thread-topic: [Xen-users] dom0 incorrect mem size

Thanks for this follow-up.
we are now seeing 511 as total memory in the xen dom0 kernel.
when I do xm info |grep memory it shows a total of 8191.
my new issue here is something with xen balloon driver.  In my vm I have configured memory = '512'
but according to the xen-debug.log and xend.log it shows the balloon drivers requesting other totals then 512. Some times more, some times less.
did I miss a configure option when I built the kernel?

From: Pasi Kärkkäinen [mailto:pasik@xxxxxx]
Sent: Fri 3/12/2010 4:33 AM
To: Robbie Garertt
Cc: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] dom0 incorrect mem size

On Thu, Mar 11, 2010 at 07:04:49PM -0500, Robbie Garertt wrote:
>    Hey all,
>    just compiled xen 3.4.2 and linux  I followed the instructions
>    on the Xen wiki to get the install running.
>    my issue here is that in my grub memnu config i set dom0_mem=512M
>    when i login to the dom0 and i do a free -m i get that the system only has
>    432 under the total section.

Try reading "xm dmesg", or capturing that to a file at boot time using a serial console.

>    booting into the stock debian kernel 2.6.26-2-amd64 kernel gives me 8192
>    free memory for i did not limit that.
>    when i run xm info |grep memory under the xen kernel I get the following.
>    total_memory           : 8191
>    free_memory            : 7578
>    node_to_memory         : node0:7578

What does "xm list" show about dom0 memory?

8GB is 8192 MB, so 8191 MB total memory sounds correct.
8191 - 7578 = 613 MB.

If dom0 has 432 MB, then there's 181 MB used for something else.
Xen hypervisor (or was it dom0 kernel?) allocates some memory as a
DMA reserve, and there's some overhead per every MB of memory, and per every vcpu.

-- Pasi

>    the server only has 8gb of memory installed which is confirmed via the
>    system bios.
>    is there anyway to figure out what is going on here?

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