[libvirt] [PATCH v2 5/5] qemu: Enable memory-backend-file.discard-data whenever possible

[Daniel P. Berrangé]

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


Regards,
Daniel
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