linux-kernel - [PATCH v6 40/51] mm: Avoid splitting THPs

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Message-Id: <20200610201345.13273-41-willy@infradead.org>
Date:   Wed, 10 Jun 2020 13:13:34 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     linux-fsdevel@...r.kernel.org
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: [PATCH v6 40/51] mm: Avoid splitting THPs

From: "Matthew Wilcox (Oracle)" <willy@...radead.org>

If the filesystem supports THPs, then do not split them before
removing them from the page cache; remove them as a unit.
---
 mm/vmscan.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 17934e03b3aa..0db62c1001f7 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1277,9 +1277,9 @@ static unsigned int shrink_page_list(struct list_head *page_list,
 				/* Adding to swap updated mapping */
 				mapping = page_mapping(page);
 			}
-		} else if (unlikely(PageTransHuge(page))) {
-			/* Split file THP */
-			if (split_huge_page_to_list(page, page_list))
+		} else if (PageTransHuge(page)) {
+			if ((!mapping || !mapping_thp_support(mapping)) &&
+			    split_huge_page_to_list(page, page_list))
 				goto keep_locked;
 		}
 
-- 
2.26.2