linux-kernel - [PATCH] memblock: Uniform initialization all reserved pages to MIGRATE

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Message-Id: <20241017064449.5235-1-suhua1@kingsoft.com>
Date: Thu, 17 Oct 2024 14:44:49 +0800
From: suhua <suhua.tanke@...il.com>
To: rppt@...nel.org,
	akpm@...ux-foundation.org
Cc: linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	suhua.tanke@...il.com,
	suhua <suhua1@...gsoft.com>
Subject: [PATCH] memblock: Uniform initialization all reserved pages to MIGRATE_MOVABLE

Currently when CONFIG_DEFERRED_STRUCT_PAGE_INIT is not set, the reserved
pages are initialized to MIGRATE_MOVABLE by default in memmap_init.

Reserved memory mainly stores the metadata of struct page. When
HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON=Y and hugepages are allocated,
the memory occupied by the struct page metadata will be freed.

Before this patch:
when CONFIG_DEFERRED_STRUCT_PAGE_INIT is not set, the freed memory was
placed on the Movable list;
When CONFIG_DEFERRED_STRUCT_PAGE_INIT=Y, the freed memory was placed on
the Unmovable list.

After this patch, the freed memory is placed on the Movable list
regardless of whether CONFIG_DEFERRED_STRUCT_PAGE_INIT is set.

Eg:
echo 500000 > /proc/sys/vm/nr_hugepages
cat /proc/pagetypeinfo

before：
Free pages count per migrate type at order       0      1      2      3      4      5      6      7      8      9     10
…
Node    0, zone   Normal, type    Unmovable     51      2      1     28     53     35     35     43     40     69   3852
Node    0, zone   Normal, type      Movable   6485   4610    666    202    200    185    208     87     54      2    240
Node    0, zone   Normal, type  Reclaimable      2      2      1     23     13      1      2      1      0      1      0
Node    0, zone   Normal, type   HighAtomic      0      0      0      0      0      0      0      0      0      0      0
Node    0, zone   Normal, type      Isolate      0      0      0      0      0      0      0      0      0      0      0
Unmovable ≈ 15GB

after：
Free pages count per migrate type at order       0      1      2      3      4      5      6      7      8      9     10
…
Node    0, zone   Normal, type    Unmovable      0      1      1      0      0      0      0      1      1      1      0
Node    0, zone   Normal, type      Movable   1563   4107   1119    189    256    368    286    132    109      4   3841
Node    0, zone   Normal, type  Reclaimable      2      2      1     23     13      1      2      1      0      1      0
Node    0, zone   Normal, type   HighAtomic      0      0      0      0      0      0      0      0      0      0      0
Node    0, zone   Normal, type      Isolate      0      0      0      0      0      0      0      0      0      0      0

Signed-off-by: suhua <suhua1@...gsoft.com>
---
 mm/mm_init.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/mm_init.c b/mm/mm_init.c
index 4ba5607aaf19..6dbf2df23eee 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -722,6 +722,10 @@ static void __meminit init_reserved_page(unsigned long pfn, int nid)
 		if (zone_spans_pfn(zone, pfn))
 			break;
 	}
+
+	if (pageblock_aligned(pfn))
+		set_pageblock_migratetype(pfn_to_page(pfn), MIGRATE_MOVABLE);
+
 	__init_single_page(pfn_to_page(pfn), pfn, zid, nid);
 }
 #else
-- 
2.34.1