Re: [Xen-users] 101th domU fails to start with "SETVCPUCONTEXT failed"

[Lennert Van Alboom <lennert@xxxxxxxxxxxxx>]

On Sun, Jan 10, 2010 at 12:30:12AM +0100, storm66@xxxxxxxxxxxxxxxx wrote:
> Le samedi 09 janvier 2010 à 21:57 +0100, Lennert Van Alboom a écrit :
> > Hello there,
> >
> >
> > We (a small hosting community) are running a steadily growing number of Xen 
> > domUs on a quad dualcore Xeon server with 64GB ram. We've got 100 running 
> > domUs at the moment. Trying to create a new one results in this error:
> > Error: (1, 'Internal error', 'launch_vm: SETVCPUCONTEXT failed (rc=-1)\n')
> >
> > If I shut down another domain, I can create one again, but the limit
> > seems to be 100 domUs. 
> > Each domU has one network interface and one or two disk devices (raid-1
> > md device consisting of two iscsi luns).
> >
> > Version of Xen is rather old: 3.2.1-amd64 (Debian). 
> >
> > Can anyone give me hint as to what causes this behaviour? The host
> > machine should be able to cope with the amount of domUs easily. I've got
> > a feeling I'm bumping into an obscure sourcecode parameter somewhere.
> >
> >
> > Thanks in advance,
> >
> >
> > Lennert
> Hello,
>
> In my thought Xen is heavily using loop devices, I had some problems
> some years ago with a system running XEN 3.0 with a kernel where the
> default loop max number was too low. 
> I didn't get that problem with newer versions.
>
> Regards
>
> JPP
Thanks for your reply. We aren't using loop devices though - only
physical ones (raid-1 md devices). 

I've checked
http://lxr.mstier.de/Xen/source/xen_3.2.1/tools/libxc/xc_dom_boot.c?v=3.2.1
for the location where it barfs - it looks to me that the failing
function is do_domctl (line 60).
This do_domctl is defined in
http://lxr.mstier.de/Xen/source/xen_3.2.1/xen/common/domctl.c?v=3.2.1
and it seems a bit over my head...

Anyone have experience with digging in the xen sourcecode that can help
me resolve this issue?


Kind regards,


Lennert

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