Re: [Xen-devel] [PATCH v2 3/3] tools/libxc: use superpages during restore of HVM guest

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Wed, Aug 23, 2017 at 10:05:37AM +0200, Olaf Hering wrote:
> On Tue, Aug 22, Olaf Hering wrote:
> 
> > In my testing I have seen the case of over-allocation. Thats why I
> > implemented the freeing of unpopulated parts. It would be nice to know
> > how many pages are actually coming. I think this info is not available.
> 
> If the receiving dom0 recognizes an over-allocation it must know how
> much memory a domU is supposed to have. Perhaps there is a way to
> retreive this info.
> 

Dom0 probably gets an error from Xen about failing to allocate memory,
but I'm not sure it can tell whether it is due to DomU trying to use
more than it should or Xen is oom.

> An interesting case is ballooning during migration. Is the new amount of
> pages per domU actually transfered to the receiving domU? If the domU is
> ballooned up the other side may see the incoming domU as over-allocated.
> If it is ballooned down pages may be missing. Was this ever considered?
> 

No, I don't think that's covered.

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