On Tue, 5 Aug 2025 at 16:26, Jason Gunthorpe <jgg@xxxxxxxxxx> wrote:
>
> David, there is another alternative to prevent this, simple though a
> bit wasteful, just allocate a bit bigger to ensure the allocation
> doesn't end on an exact PAGE_SIZE boundary?
So I don't mind adding a check for "page_section()", because at least
that makes sense.
But yes, it would also probably be a good idea to try to minimize
SPARSEMEM without VMEMMAP. I'd love to get rid of it entirely, of
course, but even if that isn't possible, I'd *really* just like people
to try to make sure that it's neve ra valid thing to try to combine
memory across different sections.
David mentioned the 1GB hugepage folios, and I really thought that
even *those* were all in one section. They *should* be.
Do we have any relevant architectures that still do SPARSEMEM without
VMEMMAP? Because if it's purely some "legacy architecture" thing (ie
x86-32), how about just saying "no 1GB hugepages for you".
Because that whole SPARSEMEM without VMEMMAP is certainly painful even
outside of nth_page, and minimizing the pain sounds sane.
Linus
