Re: [Xen-devel] Strange memory balloning problem even if balloning is disabled

[Fabio Fantoni <fabio.fantoni@xxxxxxx>]

Il 03/03/2015 12:47, Fabio Fantoni ha scritto:
> Il 03/03/2015 12:09, David Vrabel ha scritto:
> > On 03/03/15 09:05, Fabio Fantoni wrote:
> > > Il 02/03/2015 17:31, David Vrabel ha scritto:
> > > > On 02/03/15 16:23, Jan Beulich wrote:
> > > > > > > > On 02.03.15 at 16:52, <fabio.fantoni@xxxxxxx> wrote:
> > > > > > On systems with wheezy as dom0 and kernel 3.2 it seems there are no
> > > > > > visible problems.
> > > > > > After updating the kernel to 3.16 (from backports repository), after
> > > > > > starting the domUs, I get many of these errors in syslog and 
> > > > > > kern.log
> > > > > > (infinite loop):
> > > > > > xen:balloon: Cannot add additional memory (-17)
> > > > > I have a vague recollection of some fix from David aiming at
> > > > > avoiding to issue this message, but you would clearly have better
> > > > > luck getting a qualified response if you Cc-ed kernel people when
> > > > > reporting kernel problems (assuming you need explicit Cc-s at all,
> > > > > as most relevant people read the list anyway afaik) - I certainly
> > > > > can't figure by what criteria you put together the Cc list.
> > > > You need
> > > >
> > > > 3dcf63677d4eb7fdfc13290c8558c301d2588fe8 (xen/balloon: cancel 
> > > > ballooning
> > > > if adding new memory failed)
> > > > fd8b79511349efd1f0decea920f61b93acb34a75 (xen/balloon: Don't continue
> > > > ballooning when BP_ECANCELED is encountered)
> > > >
> > > > Or you can disable CONFIG_XEN_BALLOON_MEMORY_HOTPLUG.
> > > >
> > > > David
> > > Readded the other part of my initial mail that explain better the
> > > problem (also with the patch above applied)...
> > >
> > > The strange thing is that it should not use balloning because both dom0
> > > and domUs have fixed memory set and balloning disabled.
> > Ballooned pages are required to back grant mapped pages in blkback and
> > netback.
> >
> > David
> Thanks for your reply.
> Based on your reply seems I must enable balloning in dom0 (for example 
> dom0_mem=2G,max:3G) and/or xl.conf (autoballoon=1) to have it full 
> working (for grant mapped pages), is it correct?
With same dom0 I tried on different server (Dell PE T620 instead Dell PE 
T310) and after xl create of a W7 domU...
Some seconds after dom0 becomes unusable, unreachable over the network 
and not respond to commandsconnecting from drac.
I did forced powerdown and looking the logs I saw only 36mb of this 
error in 2 minutes:
xen:balloon: Cannot add additional memory (-17)

I have kernel with patch that should avoiding this 
(3.16.7-ckt4-3~bpo70+1) and in grub.cfg dom0_mem=2G,max:3G
I not found anything else strange on logs except this in dom0's logs.

If you need more informations or tests tell me and I'll post them.

Thanks for any reply and sorry for my bad english.

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