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

[Song Liu]

On Thu, May 18, 2023 at 6:24 PM Kent Overstreet
<kent.overstreet@xxxxxxxxx> wrote:
>
> 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.

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