+ mm-page_alloc-speeding-up-the-iteration-of-max_order.patch added to -mm tree

* + mm-page_alloc-speeding-up-the-iteration-of-max_order.patch added to -mm tree
@ 2020-12-05  0:39 akpm
  0 siblings, 0 replies; 2+ messages in thread
From: akpm @ 2020-12-05  0:39 UTC (permalink / raw)
  To: mm-commits, songmuchun, vbabka


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@bytedance.com>
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@bytedance.com
Fixes: d9dddbf55667 ("mm/page_alloc: prevent merging between isolated and other pageblocks")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 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@bytedance.com 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


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