Re: [PATCH v5 10/17] mm/hugetlb: switch HugeTLB to section-based vmemmap optimization

[David Hildenbrand (Arm)]

On 8/25/26 10:46, Muchun Song wrote:
> HugeTLB bootmem vmemmap optimization still carries its own early setup
> path, including pre-populating optimized mappings before the generic
> sparse-vmemmap code runs.
> 
> Now that the section-based vmemmap optimization can derive HugeTLB
> vmemmap deduplication from section metadata, HugeTLB only needs to mark
> the bootmem huge page range with the appropriate order. The generic
> sparse-vmemmap population path can then allocate and map the shared tail
> vmemmap pages without any HugeTLB-specific early population code.
> 
> Do that by setting the section order when a bootmem huge page is
> allocated and dropping the dedicated pre-HVO helpers and related
> special-casing.
> 
> This removes duplicate early setup logic and switches HugeTLB to the
> section-based vmemmap optimization path.
> 
> Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
> Acked-by: Mike Rapoport (Microsoft) <rppt@xxxxxxxxxx>
> ---
> v3:
> - Use the order-based helper for the bootmem vmemmap-optimized check
> 
> v2:
> - Collect Acked-by from Mike Rapoport
> ---
>  include/linux/hugetlb.h |  1 -
>  include/linux/mm.h      |  3 --
>  mm/hugetlb.c            | 30 ++------------
>  mm/hugetlb_vmemmap.c    | 90 +++--------------------------------------
>  mm/hugetlb_vmemmap.h    | 14 +++----
>  mm/sparse-vmemmap.c     | 31 --------------
>  mm/sparse.h             | 27 +++++++++++++
>  7 files changed, 42 insertions(+), 154 deletions(-)

Nice cleanup.

>  
> diff --git a/mm/sparse.h b/mm/sparse.h
> index e4617f9c8876..049272aba84e 100644
> --- a/mm/sparse.h
> +++ b/mm/sparse.h
> @@ -16,6 +16,24 @@ static inline unsigned int section_order(const struct mem_section *section)
>  	return section->order;
>  }
>  
> +static inline void section_set_order(struct mem_section *section, unsigned int order)
> +{
> +	VM_WARN_ON(section_order(section) && order && section_order(section) != order);
> +	section->order = order;

As raised previously "section order" is entirely unclear. If this is a compound
page order we should spell that out.


-- 
Cheers,

David