Hi, David,

On Wed, Feb 17, 2021 at 04:48:44PM +0100, David Hildenbrand wrote:

When we manage sparse memory mappings dynamically in user space - also
sometimes involving MADV_NORESERVE - we want to dynamically populate/
discard memory inside such a sparse memory region. Example users are
hypervisors (especially implementing memory ballooning or similar
technologies like virtio-mem) and memory allocators. In addition, we want
to fail in a nice way if populating does not succeed because we are out of
backend memory (which can happen easily with file-based mappings,
especially tmpfs and hugetlbfs).

Could you explain a bit more on how do you plan to use this new interface for
the virtio-balloon scenario?

Meanwhile, here you seemed to be talking about file-backed mem, however later
it sounds more like for anonymous, so I'm slightly confused.

Thanks,

-- 
Peter Xu