Re: [PATCH RFC] mm/madvise: introduce MADV_POPULATE to prefault/prealloc memory

Michal Hocko
2021-02-22T14:03:57Z

On Mon 22-02-21 14:22:37, David Hildenbrand wrote:
> > > Exactly. But for hugetlbfs/shmem ("!RAM-backed files") this is not what we
> > > want.
> >
> > OK, then I must have misread your requirements. Maybe I just got lost in
> > all the combinations you have listed.
>
> Another special case could be dax/pmem I think. You might want to fault it
> in readable/writable but not perform an actual read/write unless really
> required.
>
> QEMU phrases this as "don't cause wear on the storage backing".

Sorry for being dense here but I still do not follow. If you do not want
to read then what do you want to populate from? Only map if it is in the
page cache?
--
Michal Hocko
SUSE Labs