Re: [Qemu-devel] Some question about savem/qcow2 incremental snapshot

[Dr. David Alan Gilbert]

* Stefan Hajnoczi (address@hidden) wrote:
> On Tue, Jan 9, 2018 at 7:55 PM, Dr. David Alan Gilbert
> <address@hidden> wrote:
> >> Certain guest operations like rebooting or zeroing memory will defeat
> >> the incremental guest RAM snapshot feature.  It's worth thinking about
> >> these cases to make sure this feature would be worth it in real use
> >> cases.
> >
> > But those probably wouldn't upset an NVDimm?
> 
> If the guest dirties all RAM then the incremental snapshot feature
> degrades to a full snapshot.  I'm asking if there are common
> operations where that happens.
> 
> I seem to remember Windows guests zero all pages on cold boot.  Maybe
> that's not the case anymore.
> 
> Worth checking before embarking on this feature because it could be a
> waste of effort if it turns out real-world guests dirty all memory in
> common cases.

Right, but I'm hoping that there's some magic somewhere where an NVDimm doesn't
get zero'd because of a cold boot since that would seem to make it
volatile.

Dave

--
Dr. David Alan Gilbert / address@hidden / Manchester, UK