Ballooning is cool mechanism, but it is not overcommitment. We can say
'theoretical overcommitment' - if we starting few machines with mem=1GiB
maxmem=10GiB, we (theoretically) give every machine 10G, but this is not
overcommitment, it just limits, raised up beyond host memory.
Actual overcommitment/oversell is when sum of actually allocated memory
(as displayed by 'free' in every guest) is more then memory on host.
Xen lack of this feature and I believe this make it more pricey in term
of VPS/VDS hosting, but much better quality for end-users (domUs),
compare to OpenVZ overcommitment.
В Птн, 24/09/2010 в 16:24 -0300, Martinx - ジェームズ пишет:
> Mmm... You mean this:
> On 24 September 2010 15:49, George Shuklin <george.shuklin@xxxxxxxxx>
> Yes, It is nice technology, but it still do not allow
> swapping or overselling. :)
> В Птн, 24/09/2010 в 14:57 -0300, Martinx - ジェームズ пишет:
> > Hi!
> > The Xen 4.0 introduces the TMEM project, take a look at it:
> > http://wiki.xensource.com/xenwiki/Xen4.0
> > TMEM allows improved utilization of unused (for example
> page cache)
> > PV guest memory. more
> > information: http://oss.oracle.com/projects/tmem/
> > On 24 September 2010 14:46, George Shuklin
> > wrote:
> > You can use swap of any size at VM level (every VM
> will have
> > it own
> > swap).
> > Right now there is no way to do hypervisor swap or
> > memory.
> > В Птн, 24/09/2010 в 13:14 -0400, Boris Epstein
> > > Hello listmates,
> > >
> > > Let's say I've got a machine with 1 GB of RAM and
> I want to
> > host 3 512
> > > MB virtual machines on it? Is that possible -
> i.e., is it
> > possible to
> > > force Xen to use swap and pass it off as RAM to
> the VM's? I
> > know it is
> > > slow and inefficient but for the purposes of
> testing - is
> > that
> > > possible?
> > >
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