From: Muchun Song
mainline inclusion
from mainline-v5.11-rc1
commit 7ad69832f37e3cea8557db6df7c793905f1135e8
category: bugfix
issue: #I3ZXZF
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
-----------------------------------------------
When we free a page whose order is very close to MAX_ORDER and greater
than pageblock_order, it wastes some CPU cycles to increase max_order to
MAX_ORDER one by one and check the pageblock migratetype of that page
repeatedly especially when MAX_ORDER is much larger than pageblock_order.
We also should not be checking migratetype of buddy when "order ==
MAX_ORDER - 1" as the buddy pfn may be invalid, so adjust the condition.
With the new check, we don't need the max_order check anymore, so we
replace it.
Also adjust max_order initialization so that it's lower by one than
previously, which makes the code hopefully more clear.
Link: https://lkml.kernel.org/r/20201204155109.55451-1-songmuchun@bytedance.com
Fixes: d9dddbf55667 ("mm/page_alloc: prevent merging between isolated and other pageblocks")
Signed-off-by: Muchun Song
Acked-by: Vlastimil Babka
Reviewed-by: Oscar Salvador
Reviewed-by: David Hildenbrand
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
Signed-off-by: Tong Tiangen
Reviewed-by: Chen Wandun
Signed-off-by: Chen Jun
Signed-off-by: Yu Changchun
---
mm/page_alloc.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ff8fbc65a78d..6d189b69a9e1 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -996,7 +996,7 @@ static inline void __free_one_page(struct page *page,
struct page *buddy;
bool to_tail;
- max_order = min_t(unsigned int, MAX_ORDER, pageblock_order + 1);
+ max_order = min_t(unsigned int, MAX_ORDER - 1, pageblock_order);
VM_BUG_ON(!zone_is_initialized(zone));
VM_BUG_ON_PAGE(page->flags & PAGE_FLAGS_CHECK_AT_PREP, page);
@@ -1009,7 +1009,7 @@ static inline void __free_one_page(struct page *page,
VM_BUG_ON_PAGE(bad_range(zone, page), page);
continue_merging:
- while (order < max_order - 1) {
+ while (order < max_order) {
if (compaction_capture(capc, page, order, migratetype)) {
__mod_zone_freepage_state(zone, -(1 << order),
migratetype);
@@ -1035,7 +1035,7 @@ static inline void __free_one_page(struct page *page,
pfn = combined_pfn;
order++;
}
- if (max_order < MAX_ORDER) {
+ if (order < MAX_ORDER - 1) {
/* If we are here, it means order is >= pageblock_order.
* We want to prevent merge between freepages on isolate
* pageblock and normal pageblock. Without this, pageblock
@@ -1056,7 +1056,7 @@ static inline void __free_one_page(struct page *page,
is_migrate_isolate(buddy_mt)))
goto done_merging;
}
- max_order++;
+ max_order = order + 1;
goto continue_merging;
}
--
2.22.0
