linux-kernel - Re: [PATCH v2] mm: align larger anonymous mappings on THP boundaries

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Message-ID: <CAHbLzkr=QCD5i7X7ns5ZdakYZ3HVS4QnZGnx3UwuvDOqMR0=Wg@mail.gmail.com>
Date:   Wed, 10 Aug 2022 10:06:21 -0700
From:   Yang Shi <shy828301@...il.com>
To:     Rik van Riel <riel@...riel.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, kernel-team@...com,
        Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH v2] mm: align larger anonymous mappings on THP boundaries

On Tue, Aug 9, 2022 at 11:25 AM Rik van Riel <riel@...riel.com> wrote:
>
> Align larger anonymous memory mappings on THP boundaries by
> going through thp_get_unmapped_area if THPs are enabled for
> the current process.
>
> With this patch, larger anonymous mappings are now THP aligned.
> When a malloc library allocates a 2MB or larger arena, that
> arena can now be mapped with THPs right from the start, which
> can result in better TLB hit rates and execution time.
>
> Signed-off-by: Rik van Riel <riel@...riel.com>
> ---
> v2: avoid the chicken & egg issue with MMF_VM_HUGEPAGE (Yang Shi)

Reviewed-by: Yang Shi <shy828301@...il.com>

>
>  mm/mmap.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index c035020d0c89..1d859893436d 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -2229,6 +2229,9 @@ get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
>                  */
>                 pgoff = 0;
>                 get_area = shmem_get_unmapped_area;
> +       } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
> +               /* Ensures that larger anonymous mappings are THP aligned. */
> +               get_area = thp_get_unmapped_area;
>         }
>
>         addr = get_area(file, addr, len, pgoff, flags);
> --
> 2.37.1
>
>