On Tue, Apr 17, 2018 at 13:18:02 +0100, Daniel Berrange wrote:
On Tue, Apr 17, 2018 at 01:16:42PM +0200, Michal Privoznik wrote:
https://bugzilla.redhat.com/show_bug.cgi?id=1480668
The cases when we cannot enable this optimization are: 1) nvdimms 2) if memAccess='shared'
Otherwise it is safe to enable it.
This is basically saying that if memAccess==private, then no person/app cares about the contents of the memory-backend-file storage after QEMU has exited, because (implicitly) whatever data was in that storage is not going to be used again. While I accept that's going to be a common case, I'm wary of saying that is a 100% safe/valid assumption for every user.
I tend think it should require an explicit opt-in to turn on this behaviour
Well, we used that behaviour prior to storing the backing files in a "predictible" path as the file was unlinked right after creating it (so that some memory management software can do some magic behind our backs with that) so I don't think anybody would depend on the described behaviour.