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Subject[PATCH 1/3] mm: sparse: pass section_nr to section_mark_present
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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)
--
2.17.1
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