Re: [PATCH 12/12] mm/hugetlb: make bootmem allocation work with KHO

[Mike Rapoport <rppt@kernel.org>]

On Mon, May 25, 2026 at 05:24:09PM +0200, Pratyush Yadav wrote:
> On Sun, May 17 2026, Mike Rapoport wrote:
> > On Wed, Apr 29, 2026 at 03:39:14PM +0200, Pratyush Yadav wrote:
> >> From: "Pratyush Yadav (Google)" <pratyush@kernel.org>
> 
> So, in summary, I would like to pursue option 1 and try to make it more
> appetizing. But I would like to at least know if you hate the "extended
> scratch" (ignore the name) as a concept or only the code it results in.

Let's retry this one :)

I looked more closely, and it seems that mixing SCRATCH and SCRATCH_EXT
should be a lesser headache than going with option 4.

Tracking the changes in gigantic pages in hugetlb also does not seem
something we'd like to pursue especially considering that memory from freed
or demoted gigantic pages could be reserved.

If we add a dedicated memblock_something to allocate gigantic pages, we
can reduce branching in alloc_bootmem() to

	if (cma)
		do_cma()
	else
		do_memblock()

For hugetlb_cma we might want to teach CMA to create pre-allocated areas
and then it could reuse the same memblock API. This seems useful even
regardless of KHO.
 
-- 
Sincerely yours,
Mike.