The patch titled
Subject: mm/page_alloc: speed up the iteration of max_order
has been added to the -mm tree. Its filename is
mm-page_alloc-speeding-up-the-iteration-of-max_order.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-page_alloc-speeding-up-the-iteration-of-max_order.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-page_alloc-speeding-up-the-iteration-of-max_order.patch
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------------------------------------------------------
From: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Subject: mm/page_alloc: speed up the iteration of max_order
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@xxxxxxxxxxxxx
Fixes: d9dddbf55667 ("mm/page_alloc: prevent merging between isolated and other pageblocks")
Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
--- a/mm/page_alloc.c~mm-page_alloc-speeding-up-the-iteration-of-max_order
+++ a/mm/page_alloc.c
@@ -996,7 +996,7 @@ static inline void __free_one_page(struc
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(struc
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 @@ continue_merging:
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 @@ continue_merging:
is_migrate_isolate(buddy_mt)))
goto done_merging;
}
- max_order++;
+ max_order = order + 1;
goto continue_merging;
}
_
Patches currently in -mm which might be from songmuchun@xxxxxxxxxxxxx are
mm-memcontrol-remove-unused-mod_memcg_obj_state.patch
mm-memcg-slab-fix-return-child-memcg-objcg-for-root-memcg.patch
mm-memcg-slab-fix-use-after-free-in-obj_cgroup_charge.patch
mm-memcg-slab-rename-_lruvec_slab_state-to-_lruvec_kmem_state.patch
mm-memcontrol-make-the-slab-calculation-consistent.patch
mm-page_alloc-speeding-up-the-iteration-of-max_order.patch
mm-page_isolation-do-not-isolate-the-max-order-page.patch
