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

[Pim van Riezen <pi+lists@xxxxxxxxxxxx>]

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?

Cheers,
Pi


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