Re: [Xen-users] Xen 4.0.1 hangs when trying to create vps

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Mon, Feb 21, 2011 at 11:39:03AM +0100, Pim van Riezen wrote:
> 
> On Feb 21, 2011, at 11:19 , Pasi Kärkkäinen wrote:
> 
> > On Mon, Feb 21, 2011 at 10:52:49AM +0100, Pim van Riezen wrote:
> >> 
> >> On Feb 21, 2011, at 10:48 , Pasi Kärkkäinen wrote:
> >> 
> >>> On Wed, Feb 02, 2011 at 02:00:36PM +0100, Pim van Riezen wrote:
> >>>> Good day,
> >>>> 
> >>>> we recently migrated to Xen4.0.1 on one of our clusters. It solves a lot 
> >>>> of problem, but it also adds one. Whenever we try to xm create a guest 
> >>>> that oversteps the total amount of available memory, xend completely 
> >>>> hangs itself up and stops responding to any rpc calls..
> >>>> 
> >>>> The last lines in xend.log are:
> >>>> 
> >>>> [2011-02-02 10:00:22 8199] DEBUG (balloon:172) Balloon: tmem 
> >>>> relinquished -1 KiB of 20100116 KiB requested.
> >>>> [2011-02-02 10:00:22 8199] DEBUG (balloon:226) Balloon: 13454316 KiB 
> >>>> free; 0 to scrub; need 33554432; retries: 115.
> >>>> [2011-02-02 10:00:22 8199] DEBUG (balloon:226) Balloon: 13454316 KiB 
> >>>> free; 0 to scrub; need 33554432; retries: 210.
> >>>> 
> >>>> is there a way to recover from this?
> >>>> 
> >>> 
> >>> Did you dedicate fixed amount of memory for dom0?
> >> 
> >> Yes.
> >> 
> >>> Are you using tmem? 
> >> 
> >> No.
> >> 
> > 
> > Ok. Did you disable dom0 ballooning? 
> > http://wiki.xensource.com/xenwiki/XenBestPractices
> > 
> > It looks like xend is trying to balloon down dom0, which seems to fail and 
> > crash things.
> 
> This option was indeed not explicitly set. I think htis is a result of our 
> migration from an earlier Xen 3 install. This used to be the documentation 
> for dom0-min-mem in xend-config.sxp:
> 
> # Dom0 will balloon out when needed to free memory for domU.
> # dom0-min-mem is the lowest memory level (in MB) dom0 will get down to.
> # If dom0-min-mem=0, dom0 will never balloon out.
> 
> i.e., the "no ballooning" used to be explicitly linked to the dom0 min mem 
> and there was no enable-dom0-ballooning.
> 
> I'll fix the options in our configuration now, thanks for the heads-up.
> 
> My only suggestion left is that xend becoming completely unresponsive is 
> probably not the best response to such a configuration foul-up. Should I 
> report that as a possible bug somewhere?
> 

I'm suspecting it's actually dom0 kernel issue, and not xend issue.
If you want to investigate further and track down the actual problem, feel free.

-- Pasi


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