[CentOS-virt] centos6 and xen4 dom0 memory allocation

Peter Peltonen peter.peltonen at gmail.com
Wed Oct 19 17:37:34 EDT 2011


This is slightly OT as xen is not officially supported in EL6. But
maybe someone else is running it on centos6 as well and could help me
out here:

I have problems allocating a static amount of memory for my xen dom0.
It seems to reduce when new domUs are created, even though I *think*
ballooning is disabled. Can someone advise me what I'm doing wrong?

I have xen-4.1.1-3 installed from
http://xenbits.xen.org/people/mayoung/EL6.xen on my centos6 server. I
am running 2.6.32-131.12.1.el6.xendom0.x86_64 kernel available from
the same place. 'xl info' reports about available memory as follows:

total_memory           : 24567
free_memory            : 3698
xen_commandline        : dom0_mem=2048M

and in xend-config.sxp I have:

(dom0-min-mem 256)
(enable-dom0-ballooning no)
(total_available_memory 0)

Now one would think that I should have 2048M memory for dom0, right? I
started from there, but when starting domUs it has been reduced to
1140M even though I think ballooning is disabled and there is free
memory available? And the weird thing is that dom0 has done some

# free -mt
             total       used       free     shared    buffers     cached
Mem:          1140       1052         88          0          2         12
-/+ buffers/cache:       1038        102
Swap:         8194         85       8109
Total:        9335       1138       8197

Shutting down domUs and making more memory available does not reverse
the effect, dom0 does not allocate more memory.

What am I missing here or is my xen setup acting strangely here?

Best regards,

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