Re: [Xen-devel] How to determine memory size in HVM

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 10/06/2009 16:28, "James Harper" <james.harper@xxxxxxxxxxxxxxxx> wrote:

>> We might have to provide more info to you via xenstore to do the 100%
> right
>> thing here.
> 
> Well I think the main problem is that if you shrink the DomU and then
> reboot, you can't ever grow it again as Windows thinks it booted with
> less memory. While there is the ability to add memory to a running
> Windows machine, it is the 'hot add memory' (eg plugging in a memory
> stick) and involves ACPI and only works under the Windows Server
> Enterprise editions (which might still be useful, but probably not worth
> the headaches involved in the ACPI work). I think the other issues are
> minor in comparison to this problem.

Populate-on-demand just needs integrating properly into xend. Then we would
reboot with maxmem, and then the guest properly balloons down as soon as
your GPLPV drivers are loaded. Populate-on-demand means the guest thinks it
has maxmem allocated to it, but really memory pages are only being allocated
to it on first use. This is all implemented in Xen and at least the lowest
levels of the toolstack (libxc).

 -- Keir



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