Re: [Xen-users] Unable to instantiate additional guest domains

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Wed, Jun 15, 2016 at 10:41:33AM +0100, Vittorio Cozzolino wrote:
> Hi,
> 
> I'm currently running some stress tests to figure out how many PVs I can
> squeeze into my server with Xen. The machine has 64 vcpus (32 physical) and
> 128 GB RAM. My Domain-0 has 8 vcpus dedicated to it.
> 
> My basic PV VM is a Linux Alpine DomU with the following settings:
> 
> 
> # DomU settings
> memory = 512
> name = "tiny_alpine_51"
> vcpus = 2
> maxvcpus = 2
> 
> I have reached the point where I have 50 PV of this kind booted and ready.
> If I try to add more guests domains I receive the following error:
> 
> 
> libxl: error: libxl_dom.c:301:libxl__build_pre: Couldn't set max vcpu count
> libxl: error: libxl_create.c:1142:domcreate_rebuild_done: cannot (re-)build
> domain: -3
> libxl: error: libxl.c:1591:libxl__destroy_domid: non-existant domain 650
> libxl: error: libxl.c:1549:domain_destroy_callback: unable to destroy guest
> with domid 650
> libxl: error: libxl.c:1476:domain_destroy_cb: destruction of domain 650
> failed
> 
> Can anyone help me understand the reason behind such message (machine limit
> reached?) or how to tune my XEN hypervisor and avoid it?
> 

Hmm... I myself have tried to boot up 3000 VMs a few years back.  The
VMs were quite small in terms of memory consumption at the time of my
experiment but I don't think I encountered error like this.

The call to set max vcpus involves allocating memory from xen heap.  Do
you see anything interesting in "xl dmesg"?  You may want to increase
xen's log level to get most information of out it.

Wei.

> Best regards,
> Vittorio
> 
> 
> 
> -- 
> Vittorio Cozzolino, M.Eng.
> Technische Universität München - Institut für Informatik
> Office 01.05.051
> Boltzmannstr. 3, 85748 Garching, Germany
> Tel: +49 89 289-17356
> http://www.cm.in.tum.de/en/research-group/vittorio-cozzolino
> 
> 



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