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memblock: avoid some repeat when add new range

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The worst case is that the new memory range overlaps all existing
regions, which requires type->cnt + 1 empty struct memblock_region slots in
the type->regions array.
So if type->cnt + 1 + type->cnt is less than type->max, we can insert
regions directly rather than calculate the needed amount before the
insertion.
And becase of merge operation in the end of function, tpye->cnt will
increase slowly for many cases.

This change allows to avoid unnecessary repeat of memblock ranges traversal
for many cases when adding new memory range.

Signed-off-by: Jinyu Tang <tjytimi@163.com>
[rppt: massaged comment and changelog text]
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
This commit is contained in:
Jinyu Tang 2022-06-15 17:40:15 +08:00 committed by Mike Rapoport
parent 03c765b0e3
commit 28e1a8f4b0
1 changed files with 11 additions and 0 deletions
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11
mm/memblock.c
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@ -593,6 +593,17 @@ static int __init_memblock memblock_add_range(struct memblock_type *type,
type->total_size = size;
return 0;
}
/*
* The worst case is when new range overlaps all existing regions,
* then we'll need type->cnt + 1 empty regions in @type. So if
* type->cnt * 2 + 1 is less than type->max, we know
* that there is enough empty regions in @type, and we can insert
* regions directly.
*/
if (type->cnt * 2 + 1 < type->max)
insert = true;
repeat:
/*
* The following is executed twice. Once with %false @insert and