Re: xen ballon errors in kernel logs even if I disabled it after kernel upgrade from 3.2 to 3.14

[David Vrabel <david.vrabel@citrix.com>]

On 11/12/14 09:40, Fabio Fantoni wrote:
> Il 26/09/2014 14:02, David Vrabel ha scritto:
>> On 26/09/14 12:46, Fabio Fantoni wrote:
>>> Il 26/09/2014 12:22, David Vrabel ha scritto:
>>>> On 26/09/14 09:54, Fabio Fantoni wrote:
>>>>> Yesterday I updated wheezy kernel (3.2) to 3.14 from
>>>>> wheezy-backports to
>>>>> solves one critical network problem with new windows pv driver.
>>>>> Today I saw the kernel logs full of this error:
>>>>> xen:balloon: reserve_additional_memory: add_memory() failed: -17
>>>> Fixed by:
>>>>
>>>> 3dcf63677d4eb7fdfc13290c8558c301d2588fe8 (xen/balloon: cancel
>>>> ballooning
>>>> if adding new memory failed)
>>>>
>>>> Ballooned memory is required by backends which is why you're seeing it
>>>> even with auto-ballooning disabled.
>>>>
>>>> David
>>>>
>>> Thanks for your reply.
>>> Is correct that show it also if dom0 have fixed memory size and xl.conf
>>> have balloning disabled?
>> Yes.
>>
>>> Can this problem cause a crash or other important aftermath?
>> No. It's harmless.
>>
>>> Can you apply or request the backport of this fix to stable branchs?
>> No. A fix for a harmless log message is not critical enough for stable.
>>
>> David
> 
> Thanks for your reply.
> New debian kernel is freezed to 3.16 version without this fix
> (3.16.7-ckt2-1), I not found a workaround for it, even with dom0 mem
> fixed and autoballoning  disabled I still have big syslog and kern.log
> full of these messages when I start 1 or more domUs that make difficult
> see other parts of logs.
> And another strange thing that I not understand is why older kernel
> (3.2) not have this problem.
> Someone has advices about it please?

You can workaround it by pre-ballooning dom0 with a Xen command line
option such as dom0_mem=4G,max:5G

Don't have too much ballooned memory or dom0 may run out of memory and
not boot or run very slowly.

You can also disable XEN_BALLOON_MEMORY_HOTPLUG.

David