linux-kernel - [PATCH v2 3/7] mm: shmem: add THP validation for PMD-mapped THP related statistics

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Message-Id: <b546be09a3129a69c4b645c7ae2a6d760a26091c.1715571279.git.baolin.wang@linux.alibaba.com>
Date: Mon, 13 May 2024 13:08:13 +0800
From: Baolin Wang <baolin.wang@...ux.alibaba.com>
To: akpm@...ux-foundation.org,
	hughd@...gle.com
Cc: willy@...radead.org,
	david@...hat.com,
	ioworker0@...il.com,
	wangkefeng.wang@...wei.com,
	ying.huang@...el.com,
	21cnbao@...il.com,
	ryan.roberts@....com,
	shy828301@...il.com,
	ziy@...dia.com,
	baolin.wang@...ux.alibaba.com,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 3/7] mm: shmem: add THP validation for PMD-mapped THP related statistics

In order to extend support for mTHP, add THP validation for PMD-mapped THP
related statistics to avoid statistical confusion.

Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
Reviewed-by: Barry Song <v-songbaohua@...o.com>
---
 mm/shmem.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index e4483c4596a8..a383ea9a89a5 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1661,7 +1661,7 @@ static struct folio *shmem_alloc_and_add_folio(gfp_t gfp,
 			return ERR_PTR(-E2BIG);
 
 		folio = shmem_alloc_hugefolio(gfp, info, index, HPAGE_PMD_ORDER);
-		if (!folio)
+		if (!folio && pages == HPAGE_PMD_NR)
 			count_vm_event(THP_FILE_FALLBACK);
 	} else {
 		pages = 1;
@@ -1679,7 +1679,7 @@ static struct folio *shmem_alloc_and_add_folio(gfp_t gfp,
 		if (xa_find(&mapping->i_pages, &index,
 				index + pages - 1, XA_PRESENT)) {
 			error = -EEXIST;
-		} else if (huge) {
+		} else if (pages == HPAGE_PMD_NR) {
 			count_vm_event(THP_FILE_FALLBACK);
 			count_vm_event(THP_FILE_FALLBACK_CHARGE);
 		}
@@ -2045,7 +2045,8 @@ static int shmem_get_folio_gfp(struct inode *inode, pgoff_t index,
 		folio = shmem_alloc_and_add_folio(huge_gfp,
 				inode, index, fault_mm, true);
 		if (!IS_ERR(folio)) {
-			count_vm_event(THP_FILE_ALLOC);
+			if (folio_test_pmd_mappable(folio))
+				count_vm_event(THP_FILE_ALLOC);
 			goto alloced;
 		}
 		if (PTR_ERR(folio) == -EEXIST)
-- 
2.39.3