Re: [Xen-users] dom0 incorrect mem size

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Thu, Mar 11, 2010 at 07:04:49PM -0500, Robbie Garertt wrote:
>    Hey all,
> 
>    just compiled xen 3.4.2 and linux 2.6.31.12.  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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