linux-kernel - [PATCH v2 2/9] mm/vmscan: remove unneeded can_split_huge

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Message-ID: <20220409093500.10329-3-linmiaohe@huawei.com>
Date:   Sat, 9 Apr 2022 17:34:53 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     <akpm@...ux-foundation.org>
CC:     <ying.huang@...el.com>, <songmuchun@...edance.com>,
        <hch@...radead.org>, <willy@...radead.org>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>, <linmiaohe@...wei.com>
Subject: [PATCH v2 2/9] mm/vmscan: remove unneeded can_split_huge_page check

We don't need to check can_split_folio() because folio_maybe_dma_pinned()
is checked before. It will avoid the long term pinned pages to be swapped
out. And we can live with short term pinned pages. Without can_split_folio
checking we can simplify the code. Also activate_locked can be changed to
keep_locked as it's just short term pinning.

Suggested-by: Huang, Ying <ying.huang@...el.com>
Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
---
 mm/vmscan.c | 22 ++++++++--------------
 1 file changed, 8 insertions(+), 14 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 4a76be47bed1..01f5db75a507 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1711,20 +1711,14 @@ static unsigned int shrink_page_list(struct list_head *page_list,
 					goto keep_locked;
 				if (folio_maybe_dma_pinned(folio))
 					goto keep_locked;
-				if (PageTransHuge(page)) {
-					/* cannot split THP, skip it */
-					if (!can_split_folio(folio, NULL))
-						goto activate_locked;
-					/*
-					 * Split pages without a PMD map right
-					 * away. Chances are some or all of the
-					 * tail pages can be freed without IO.
-					 */
-					if (!folio_entire_mapcount(folio) &&
-					    split_folio_to_list(folio,
-								page_list))
-						goto activate_locked;
-				}
+				/*
+				 * Split pages without a PMD map right
+				 * away. Chances are some or all of the
+				 * tail pages can be freed without IO.
+				 */
+				if (PageTransHuge(page) && !folio_entire_mapcount(folio) &&
+				    split_folio_to_list(folio, page_list))
+					goto keep_locked;
 				if (!add_to_swap(page)) {
 					if (!PageTransHuge(page))
 						goto activate_locked_split;
-- 
2.23.0