On Mon, Sep 01, 2025 at 07:02:46PM +0000, Pasha Tatashin wrote:
> > >> > This really wants some luo helper
> > >> >
> > >> > 'luo alloc array'
> > >> > 'luo restore array'
> > >> > 'luo free array'
> > >>
> > >> We can just add kho_{preserve,restore}_vmalloc(). I've drafted it here:
> > >> https://git.kernel.org/pub/scm/linux/kernel/git/rppt/linux.git/log/?h=kho/vmalloc/v1
> > >
> > > The patch looks okay to me, but it doesn't support holes in vmap
> > > areas. While that is likely acceptable for vmalloc, it could be a
> > > problem if we want to preserve memfd with holes and using vmap
> > > preservation as a method, which would require a different approach.
> > > Still, this would help with preserving memfd.
> >
> > I agree. I think we should do it the other way round. Build a sparse
> > array first, and then use that to build vmap preservation. Our emails
>
> Yes, sparse array support would help both: vmalloc and memfd preservation.
Why? vmalloc is always full popoulated, no sparseness..
And again in real systems we expect memfd to be fully populated too.
I wouldn't invest any time in something like this right now. Just be
inefficient if there is sparseness for some reason.
Jason
