On 13/12/2013 16:06, Prateek Sharma wrote:> Hello all,
> I was wondering if there is an existing mechanism in Xen for
> restoring a saved/checkpointed VM lazily. By that, I mean that the
> pages of the VM should be mapped only on access.
> Currently, restoring a VM from a snapshot seems to take a long
> time [~20 seconds for 2 GB].
> Assuming that there is no lazy-restore functionality, what would
> be a good way to implement this? Using parts of Xen-paging? Snowflock?
> Something else?
>
> Thanks!
> --Prateek
There is no current mechanism which I am aware of. I recall a few
academic papers looking in to the possibility, but no code as a result.
The restoring from a shapshot has a number of large inefficiencies in
the datapath in the privcmd driver. Fixing these would make quite an
improvement on those 20 seconds, which I suspect might be a rather
easier improvement than implementing lazy restore.
Having said that, if you are looking for a project to do, I suspect the
xen-paging infrastructure would be able to be used for lazy restore,
although Andres (author of xen-paging, CC''d) will likely be able to
speak rather more about the feasibility of it.
~Andrew