Re: [PATCH v5 03/12] mm/sparse-vmemmap: introduce CONFIG_VMEMMAP_OPTIMIZATION

["David Hildenbrand (Arm)" <david@kernel.org>]

On 9/27/26 04:54, Muchun Song wrote:
> The section-based vmemmap optimization infrastructure is guarded by
> CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP, but it can also be used by
> ZONE_DEVICE users that set dev_pagemap::vmemmap_shift. Introduce
> CONFIG_VMEMMAP_OPTIMIZATION as a common config for the shared
> infrastructure.
> 
> Select the new option from HUGETLB_PAGE_OPTIMIZE_VMEMMAP and from
> ZONE_DEVICE when the architecture opts in to DAX vmemmap optimization,
> and use it to guard the generic sparse-vmemmap state and helpers.
> 
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> Acked-by: Qi Zheng <qi.zheng@linux.dev>
> Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> ---
> v5:
> - Move this patch after the shared tail-page factoring.
> - Select VMEMMAP_OPTIMIZATION from ZONE_DEVICE instead of DEV_DAX,
>   covering all users of dev_pagemap::vmemmap_shift, reported by
>   Sashiko.
> 
> v4:
> - Rename SPARSEMEM_VMEMMAP_OPTIMIZATION to VMEMMAP_OPTIMIZATION
>   (suggested by Mike Rapoport)
> - Collect Acked-by from Mike Rapoport
> 
> v2:
> - Fix SPARSEMEM_VMEMMAP_OPTIMIZATION being selected without SPARSEMEM_VMEMMAP
>   reported by Sashiko.
> - Add an explicit DEV_DAX dependency on ZONE_DEVICE
> - Collect Acked-by from Qi Zheng
> ---
>  arch/x86/entry/vdso/vdso32/fake_32bit_build.h |  2 +-
>  fs/Kconfig                                    |  1 +
>  include/linux/mm.h                            |  3 +++
>  include/linux/mmzone.h                        | 10 +++++-----
>  include/linux/page-flags.h                    |  5 ++---
>  mm/Kconfig                                    |  5 +++++
>  mm/sparse-vmemmap.c                           |  2 +-
>  mm/sparse.h                                   |  6 +++---
>  8 files changed, 21 insertions(+), 13 deletions(-)
> 
> diff --git a/arch/x86/entry/vdso/vdso32/fake_32bit_build.h b/arch/x86/entry/vdso/vdso32/fake_32bit_build.h
> index bc3e549795c3..72a92cb9b53d 100644
> --- a/arch/x86/entry/vdso/vdso32/fake_32bit_build.h
> +++ b/arch/x86/entry/vdso/vdso32/fake_32bit_build.h
> @@ -11,7 +11,7 @@
>  #undef CONFIG_PGTABLE_LEVELS
>  #undef CONFIG_ILLEGAL_POINTER_VALUE
>  #undef CONFIG_SPARSEMEM_VMEMMAP
> -#undef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
> +#undef CONFIG_VMEMMAP_OPTIMIZATION
>  #undef CONFIG_NR_CPUS
>  #undef CONFIG_PARAVIRT_XXL
>  
> diff --git a/fs/Kconfig b/fs/Kconfig
> index d1c210c6508f..1454b7fe9641 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -278,6 +278,7 @@ config HUGETLB_PAGE_OPTIMIZE_VMEMMAP
>  	def_bool HUGETLB_PAGE
>  	depends on ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP
>  	depends on SPARSEMEM_VMEMMAP
> +	select VMEMMAP_OPTIMIZATION

Acked-by: David Hildenbrand (Arm) <david@kernel.org>

Is there a path to remove HUGETLB_PAGE_OPTIMIZE_VMEMMAP, and to merge
ARCH_WANT_OPTIMIZE_DAX_VMEMMAP+ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP into a
ARCH_SUPPORTS_VMEMMAP_OPTIMIZATION?


-- 
Cheers,

David