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mm/page_alloc: add some detailed comments in can_steal_fallback

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[akpm@linux-foundation.org: tweak grammar, fit to 80 cols]
Link: https://lkml.kernel.org/r/20240920122030.159751-1-gxxa03070307@gmail.com
Signed-off-by: gaoxiang17 <gaoxiang17@xiaomi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
gaoxiang17 2024-09-20 20:20:30 +08:00 committed by Andrew Morton
parent 5f1c8108e7
commit 6025ea5abb
1 changed files with 8 additions and 0 deletions
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8
mm/page_alloc.c
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@ -1855,6 +1855,14 @@ static bool can_steal_fallback(unsigned int order, int start_mt)
if (order >= pageblock_order)
return true;
/*
* Movable pages won't cause permanent fragmentation, so when you alloc
* small pages, you just need to temporarily steal unmovable or
* reclaimable pages that are closest to the request size. After a
* while, memory compaction may occur to form large contiguous pages,
* and the next movable allocation may not need to steal. Unmovable and
* reclaimable allocations need to actually steal pages.
*/
if (order >= pageblock_order / 2 ||
start_mt == MIGRATE_RECLAIMABLE ||
start_mt == MIGRATE_UNMOVABLE ||