RE: [Xen-devel] Re: PROBLEM: Xen ballon driver seems to be broken in 2.6.26

["Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx>]

Jeremy --

A patch was made in Xen to the balloon driver a few months ago
to avoid this problem.  The patch should probably be applied
to the balloon driver in upstream Linux.

Nemeth --

What is your "newest" Xen version?  If 3.2, the balloon driver fix
isn't there yet, but I have a bash-script workaround.  See
tools/xenballoond in xen-unstable.

Dan

> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
> [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx]On Behalf Of Jeremy
> Fitzhardinge
> Sent: Tuesday, July 22, 2008 12:03 PM
> To: Németh Tamás
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx; jeremy@xxxxxxxxxxxxx
> Subject: [Xen-devel] Re: PROBLEM: Xen ballon driver seems to be broken
> in 2.6.26
> 
> 
> Németh Tamás wrote:
> > I use openSUSE 10.3 both for dom0 and domU, but the kernels 
> and the entire Xen 
> > system (hypervisor, tools and dom0 kernel) is replaced by 
> the newest version 
> > downloadable from xen.org. Every component is compiled from 
> source. The 
> > hypervisor is 64 bit, and the dom0 and domU systems are 32 
> bit, PAE. The domU 
> > kernel is the vanilla 2.6.26. It's OK, that migration, 
> save, restore, etc. 
> > don't work, as you plan the support for these features to 
> be included in 
> > 2.6.27 AFAIK. (BTW, when will you include the domU support 
> for x86_64 and CPU 
> > hotplug?) But:
> >
> > The balloon driver also seems to be broken. If i decrease 
> the amount of memory 
> > in domU, it becomes immediately almost unresponsive. I can 
> ping the domU, and 
> > even Xvnc continues to operate (the "screen" of domU 
> changes, the KDE clock 
> > continues to count the seconds), but i cannot start new 
> programs. Sadly it 
> > includes the fact that i can't even run dmesg. Neither the 
> output of 'xm 
> > console'  gives any error message. When i destroy and 
> restart the domU then, 
> > i cannot find anything about the crash in 
> /var/log/messages. When i try to 
> > start a new program, then the domU totally hangs finally, 
> the KDE clock 
> > stops, and it cannot be shut down (only destroyed).
> >   
> 
> So that's consistent with the balloon driver 
> over-aggressively shrinking 
> the domain, until there's no memory left to do anything.  The balloon 
> driver has no safety checks to prevent that from happening.
> 
> What value are you setting the target size to?  Are you using 
> the right 
> units?
> 
>     J
> 
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