linux-kernel - [PATCH v7 01/10] mm: Allow deferred splitting of arbitrary anon large folios

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Message-Id: <20231115132734.931023-2-ryan.roberts@arm.com>
Date:   Wed, 15 Nov 2023 13:27:25 +0000
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>,
        Catalin Marinas <catalin.marinas@....com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Yang Shi <shy828301@...il.com>,
        "Huang, Ying" <ying.huang@...el.com>, Zi Yan <ziy@...dia.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Itaru Kitayama <itaru.kitayama@...il.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        John Hubbard <jhubbard@...dia.com>,
        David Rientjes <rientjes@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Hugh Dickins <hughd@...gle.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>
Cc:     Ryan Roberts <ryan.roberts@....com>, linux-mm@...ck.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH v7 01/10] mm: Allow deferred splitting of arbitrary anon large folios

In preparation for the introduction of anonymous small-sized THP, 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.

Reviewed-by: Yu Zhao <yuzhao@...gle.com>
Reviewed-by: Yin Fengwei <fengwei.yin@...el.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@...radead.org>
Reviewed-by: David Hildenbrand <david@...hat.com>
Signed-off-by: Ryan Roberts <ryan.roberts@....com>
---
 mm/rmap.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/rmap.c b/mm/rmap.c
index 7a27a2b41802..49e4d86a4f70 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1488,11 +1488,11 @@ void page_remove_rmap(struct page *page, struct vm_area_struct *vma,
 		__lruvec_stat_mod_folio(folio, idx, -nr);
 
 		/*
-		 * Queue anon THP for deferred split if at least one
+		 * Queue anon large folio for deferred split if at least one
 		 * 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