Re: [PATCH] mm/mm_init: remove zone_absent_pages_in_node()

[Mike Rapoport <rppt@kernel.org>]

On Mon, Aug 31, 2026 at 08:30:40PM +0900, Sang-Heon Jeon wrote:
> Hi,
> 
> On Mon, Aug 31, 2026 at 4:37 PM Mike Rapoport <rppt@kernel.org> wrote:
> >
> > > zone_absent_pages_in_node() returns 0 when the zone is empty and
> > > otherwise calls __absent_pages_in_range(), which already returns 0 for
> > > an empty range.
> >
> > Right, but it loops over memblock memory for an empty zone to get that 0
> 
> Indeed. How about adding an early return in __absent_pages_in_range()
> to avoid unnecessary iteration? I just want to remove the wrapper,
> which never uses its zone_type argument since eb0e5b61369f
> ("mm/mm_init: don't overlap NORMAL and MOVABLE zones with
> kernelcore=mirror")
> 
>         unsigned long nr_absent = range_end_pfn - range_start_pfn;
>         unsigned long start_pfn, end_pfn;
>         int i;
> 
> +       if (!nr_absent)

Yes, just please add a comment:
	
	/* range is empty, nothing to do */

> +               return 0;
> +
>         for_each_mem_pfn_range(i, nid, &start_pfn, &end_pfn, NULL) {
>                 start_pfn = clamp(start_pfn, range_start_pfn, range_end_pfn);
>                 end_pfn = clamp(end_pfn, range_start_pfn, range_end_pfn);
> 
> > --
> > Sincerely yours,
> > Mike.
> >

-- 
Sincerely yours,
Mike.