linux-kernel - [PATCH 06/12] mm/vmscan: Optimise shrink_page

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Message-Id: <20220116121822.1727633-7-willy@infradead.org>
Date:   Sun, 16 Jan 2022 12:18:16 +0000
From:   "Matthew Wilcox (Oracle)" <willy@...radead.org>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>
Subject: [PATCH 06/12] mm/vmscan: Optimise shrink_page_list for non-PMD-sized folios

A large folio which is smaller than a PMD does not need to do the extra
work in try_to_unmap() of trying to split a PMD entry.

Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
---
 mm/vmscan.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 45665874082d..3181bf2f8a37 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1754,7 +1754,8 @@ static unsigned int shrink_page_list(struct list_head *page_list,
 			enum ttu_flags flags = TTU_BATCH_FLUSH;
 			bool was_swapbacked = PageSwapBacked(page);
 
-			if (unlikely(PageTransHuge(page)))
+			if (PageTransHuge(page) &&
+					thp_order(page) >= HPAGE_PMD_ORDER)
 				flags |= TTU_SPLIT_HUGE_PMD;
 
 			try_to_unmap(page, flags);
-- 
2.34.1