RE: [Xen-devel] Uses of &frame_table[xfn]

["Magenheimer, Dan (HP Labs Fort Collins)" <dan.magenheimer@xxxxxx>]

> > On a related note, I'm not clear on the relationship between
> > the "memory" variable in xmdefconfig and the two reservation
> > variables needed for ballooning (not sure what they are named,
> > but call them max_reservation and initial_reservation).  Which
> > of these latter correspond to "memory" in xmdefconfig and how
> > does the other get determined?
> 
> For unprivileged guests, Xend sets both the maximum and 
> current reservation to
> the configured "memory" value, when a domain is created.  
> Subsequent calls to
> xm mem-set set the current reservation, and leave the maximum 
> alone.  Calls to
> xm mem-max set the maximum (and reducing the maximum without 
> thought is a good
> way to crash your guest).
> 
> For dom0, the initial values are set from the kernel command 
> line, and the
> current reservation is altered if memory is needed for domain 
> creation,
> migration, etc.

Thanks for the reply.  This is starting to make sense.

With the balloon driver still unimplemented, I have seen
messages (from xend?) that /proc/xen/balloon can't be
opened.  This occurs when I try to create a domain such that
the sum of memory of all launched domains (including dom0)
exceeds the total machine memory on the machine.

So when I get this message, is xend trying to balloon memory
from dom0?  Or is this the point where xend(?) tries
to do the xm mem-set to balloon some memory away from a
domU (and, if so, how does it decide which one(s) to steal
memory from)?

Thanks,
Dan

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