Re: [RFC PATCH 1/5] mm: intorduce __GFP_UNMAPPED and unmapped_alloc()

[Kent Overstreet]

On Thu, May 18, 2023 at 01:51:08PM -0700, Song Liu wrote:
 
> To allocate memory for text, we will allocate 2MiB, make it ROX, and then
> use it for many small allocations. IIUC, buddy allocator will use unallocated
> parts of this page for metadata. I guess this may be a problem, as the
> whole page is ROX now, and we have to use text_poke to write to it.

The standard kernel buddy allocator does _not_ store anything in the
page itself - because the page might be a highmem page.

That's also why I went with the bitmap for my slab allocator; standard
kernel slab allocator stores a freelist ptr in free objects.