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SubjectRe: [PATCH 1/3] mm: sparse: pass section_nr to section_mark_present
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On 02.07.21 11:41, Ohhoon Kwon wrote:
> With CONFIG_SPARSEMEM_EXTREME enabled, __section_nr() which converts
> mem_section to section_nr could be costly since it iterates all
> section roots to check if the given mem_section is in its range.
>
> On the other hand, __nr_to_section() which converts section_nr to
> mem_section can be done in O(1).
>
> Let's pass section_nr instead of mem_section ptr to
> section_mark_present() in order to reduce needless iterations.
>
> Signed-off-by: Ohhoon Kwon <ohoono.kwon@samsung.com>
> ---
> mm/sparse.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/mm/sparse.c b/mm/sparse.c
> index 55c18aff3e42..4a2700e9a65f 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -186,13 +186,14 @@ void __meminit mminit_validate_memmodel_limits(unsigned long *start_pfn,
> * those loops early.
> */
> unsigned long __highest_present_section_nr;
> -static void section_mark_present(struct mem_section *ms)
> +static void section_mark_present(unsigned long section_nr)
> {
> - unsigned long section_nr = __section_nr(ms);
> + struct mem_section *ms;
>
> if (section_nr > __highest_present_section_nr)
> __highest_present_section_nr = section_nr;
>
> + ms = __nr_to_section(section_nr);
> ms->section_mem_map |= SECTION_MARKED_PRESENT;
> }
>
> @@ -279,7 +280,7 @@ static void __init memory_present(int nid, unsigned long start, unsigned long en
> if (!ms->section_mem_map) {
> ms->section_mem_map = sparse_encode_early_nid(nid) |
> SECTION_IS_ONLINE;
> - section_mark_present(ms);
> + section_mark_present(section);
> }
> }
> }
> @@ -933,7 +934,7 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn,
>
> ms = __nr_to_section(section_nr);
> set_section_nid(section_nr, nid);
> - section_mark_present(ms);
> + section_mark_present(section_nr);
>
> /* Align memmap to section boundary in the subsection case */
> if (section_nr_to_pfn(section_nr) != start_pfn)
>

Fine for me either like this, or as Michal suggested. It's an internal
helper either way.

Reviewed-by: David Hildenbrand <david@redhat.com>

--
Thanks,

David / dhildenb

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