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References: <20210407030548.189104-1-yanfei.xu@windriver.com> <20210407030548.189104-3-yanfei.xu@windriver.com>
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From:   Yang Shi <shy828301@gmail.com>
Date:   Wed, 7 Apr 2021 14:40:56 -0700
Message-ID: <CAHbLzkqR28PW9eYJAXCjXBL+=cxQDXFrXiPfDkxCDYPB+1HgiA@mail.gmail.com>
Subject: Re: [PATCH v2 2/2] mm: khugepaged: check MMF_DISABLE_THP ahead of
 iterating over vmas
To:     "Xu, Yanfei" <yanfei.xu@windriver.com>
Cc:     Linux MM <linux-mm@kvack.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Tue, Apr 6, 2021 at 8:06 PM <yanfei.xu@windriver.com> wrote:
>
> From: Yanfei Xu <yanfei.xu@windriver.com>
>
> We could check MMF_DISABLE_THP ahead of iterating over all of vma.
> Otherwise if some mm_struct contain a large number of vma, there will
> be amounts meaningless cpu cycles cost.

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

>
> Signed-off-by: Yanfei Xu <yanfei.xu@windriver.com>
> ---
>  mm/khugepaged.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index a6012b9259a2..f4ad25a7db55 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -2094,6 +2094,8 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
>          */
>         if (unlikely(!mmap_read_trylock(mm)))
>                 goto breakouterloop_mmap_lock;
> +       if (test_bit(MMF_DISABLE_THP, &mm->flags))
> +               goto breakouterloop;
>         if (likely(!khugepaged_test_exit(mm)))
>                 vma = find_vma(mm, khugepaged_scan.address);
>
> --
> 2.27.0
>