linux-kernel - Re: [PATCH] mm: migrate: drop redundant anonymous statistics for file folios migration

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Message-ID: <CAGsJ_4x53qO1r=6=gjkZQWvc2xYR8V-t4d3t4V4o9qFobqW2-Q@mail.gmail.com>
Date: Thu, 5 Dec 2024 18:00:14 +1300
From: Barry Song <21cnbao@...il.com>
To: Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc: akpm@...ux-foundation.org, david@...hat.com, ying.huang@...ux.alibaba.com, 
	ziy@...dia.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: migrate: drop redundant anonymous statistics for file
 folios migration

On Thu, Dec 5, 2024 at 4:54 PM Baolin Wang
<baolin.wang@...ux.alibaba.com> wrote:
>
> Commit 5d65c8d758f2 ("mm: count the number of anonymous THPs per size") adds
> a new anonymous counter per THP size, however, when folio_mapping() is not NULL
> during folio migration, it means this is not an anonymous folio, so remove the
> redundant anonymous statistics in this case.

why? Are you sure anon folios won't call __folio_migrate_mapping()?
folio->mapping is PAGE_MAPPING_ANON for anon folios.

static __always_inline bool folio_test_anon(const struct folio *folio)
{
        return ((unsigned long)folio->mapping & PAGE_MAPPING_ANON) != 0;
}

>
> Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> ---
>  mm/migrate.c | 2 --
>  1 file changed, 2 deletions(-)
>
> diff --git a/mm/migrate.c b/mm/migrate.c
> index e9e00d1d1d19..d7fdfdd23fd0 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -523,8 +523,6 @@ static int __folio_migrate_mapping(struct address_space *mapping,
>          */
>         newfolio->index = folio->index;
>         newfolio->mapping = folio->mapping;
> -       if (folio_test_anon(folio) && folio_test_large(folio))
> -               mod_mthp_stat(folio_order(folio), MTHP_STAT_NR_ANON, 1);
>         folio_ref_add(newfolio, nr); /* add cache reference */
>         if (folio_test_swapbacked(folio)) {
>                 __folio_set_swapbacked(newfolio);
> --
> 2.39.3
>

Thanks
Barry