linux-kernel - Re: [PATCH v6 1/9] mm: Allow deferred splitting of arbitrary anon large folios

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Message-ID: <65867977-ac07-092e-6831-91543bb2da77@redhat.com>
Date:   Thu, 5 Oct 2023 10:19:06 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Ryan Roberts <ryan.roberts@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        Yin Fengwei <fengwei.yin@...el.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>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v6 1/9] mm: Allow deferred splitting of arbitrary anon
 large folios

On 29.09.23 13:44, Ryan Roberts wrote:
> 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.
> 
> 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 9f795b93cf40..8600bd029acf 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -1446,11 +1446,11 @@ 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);
>   	}

This patch can be picked up early I think.

-- 
Cheers,

David / dhildenb