Re: [Xen-users] Unstable/inconsistent auto-start of domUs under Xen-4.8/Linux-4.9

[Daniel Widenfalk <Daniel@xxxxxxxxxxxx>]

On 2017-03-10 13:40, Simon Hobson wrote:
> Daniel Widenfalk <Daniel@xxxxxxxxxxxx> wrote:
>
> > 2) Disable balooning on Dom0. My Dom0 will never run anything memory
> >   intensive so limiting it to, say, 4GB would not be a severe
> >   restriction.
> Common advice is to hard-wire Dom0 to a fixed memory allocation via a dom0_mem 
> statement in your grub config. I have this in mine :
> multiboot /xen-4.1-amd64.gz placeholderdom0_mem=512M dom0_max_vcpus=1 
> dom0_vcpus_pin=true
>
> which in Debian comes from an entry in /etc/default/grub of
> GRUB_CMDLINE_XEN_DEFAULT="dom0_mem=512M dom0_max_vcpus=1 dom0_vcpus_pin=true"
>
>
> One thought is that you've a race condition where you've multiple VMs all 
> causing massive ballooning in Dom0 - and Xen is timing out because it can't get 
> the memory fast enough. I;d have thought something would show in the logs for 
> that though.
> Apart from this, setting Dom0 memory is more efficient as various kernel 
> structures are sized at boot time based on memory size. So having Dom0 working 
> with a fixed smaller memory will reduce the size of these structures. Don't 
> know how much memory this actually releases ...
Many thanks for the quick reply. I disabled balooning on dom0 and now
all the domUs start up cleanly on re-boot.

Regards
/Daniel W

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