[CentOS-virt] Issue with dom0 xen ballooning

Tim Verhoeven tim.verhoeven.be at gmail.com
Wed Feb 20 16:14:40 UTC 2008

On Wed, Feb 20, 2008 at 5:08 PM, Frederic SOULIER
<frederic.soulier at univ-tlse1.fr> wrote:
>  I'm having issue with my Centos 5.1 /Xen installation.
>  I'm having  some  dom0 running 2.6.18-53.1.6.el5xen (x86_64).
>  On the dom0 where the load is high (more than 70% of total system memory
>  consumed by dom0 and domU) we have a  lot of  "memory squeeze ".
>  The result is that the domU seems to be blocked (no network/no disk
>  acces/ etc....).
>  Looking for a solution in xen user list, it seems the problem come from
>  dom0 xen ballooning.
>  With this option the dom0 attempt to use the maximum of the system
>  memory and "balloon" is memory when new domU needs memory.
>  To resolve it, we have to fix the dom0 memory usage to avoid dom0
>  ballooning and crash in our production environnemnt.
>  The solution seems to pass a parameter at xen boot time (in grub) to
>  limit dom0 memory usage : "  dom0_mem=256M "
>  As anyone encounter this type of problems ?
>  Is there any other solution than limitting dom0 memory usage ?

I did not see the problems you are having but I have a set of Xen
hosts and by default I limit the memory usage of the dom0 to 512MB
using the dom0_mem option that you mentioned. In my case the dom0's
are not doing anything so why do they need the memory in the first
place ? That is why I've limited my dom0's like this by default, I
consider this a good practice for these kinds of setups


Tim Verhoeven - tim.verhoeven.be at gmail.com - 0479 / 88 11 83

Hoping the problem magically goes away by ignoring it is the
"microsoft approach to programming" and should never be allowed.
(Linus Torvalds)

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