linux-kernel - [PATCH v1 1/3] mm: Allow deferred splitting of arbitrary large anon folios

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Message-Id: <20230717143110.260162-2-ryan.roberts@arm.com>
Date:   Mon, 17 Jul 2023 15:31:08 +0100
From:   Ryan Roberts <ryan.roberts@....com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        Yin Fengwei <fengwei.yin@...el.com>,
        David Hildenbrand <david@...hat.com>,
        Yu Zhao <yuzhao@...gle.com>, Yang Shi <shy828301@...il.com>,
        "Huang, Ying" <ying.huang@...el.com>, Zi Yan <ziy@...dia.com>
Cc:     Ryan Roberts <ryan.roberts@....com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: [PATCH v1 1/3] mm: Allow deferred splitting of arbitrary large anon folios

In preparation for the introduction of large folios for anonymous
memory, we would like to be able to split them when they have unmapped
subpages, in order to free those unused pages under memory pressure. So
remove the artificial requirement that the large folio needed to be at
least PMD-sized.

Signed-off-by: Ryan Roberts <ryan.roberts@....com>
Reviewed-by: Yu Zhao <yuzhao@...gle.com>
Reviewed-by: Yin Fengwei <fengwei.yin@...el.com>
---
 mm/rmap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/rmap.c b/mm/rmap.c
index 0c0d8857dfce..2baf57d65c23 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1430,7 +1430,7 @@ void page_remove_rmap(struct page *page, struct vm_area_struct *vma,
 		 * page of the folio is unmapped and at least one page
 		 * is still mapped.
 		 */
-		if (folio_test_pmd_mappable(folio) && folio_test_anon(folio))
+		if (folio_test_large(folio) && folio_test_anon(folio))
 			if (!compound || nr < nr_pmdmapped)
 				deferred_split_folio(folio);
 	}
-- 
2.25.1