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Subject: Re: [PATCHv3, RESEND 4/8] khugepaged: Drain LRU add pagevec after
 swapin
To:     "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        akpm@linux-foundation.org, Andrea Arcangeli <aarcange@redhat.com>
Cc:     Zi Yan <ziy@nvidia.com>, Ralph Campbell <rcampbell@nvidia.com>,
        John Hubbard <jhubbard@nvidia.com>,
        William Kucharski <william.kucharski@oracle.com>,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
References: <20200413125220.663-1-kirill.shutemov@linux.intel.com>
 <20200413125220.663-5-kirill.shutemov@linux.intel.com>
From:   Yang Shi <yang.shi@linux.alibaba.com>
Message-ID: <602d9624-1a41-611f-bba9-f38806be9c33@linux.alibaba.com>
Date:   Wed, 15 Apr 2020 13:32:59 -0700
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On 4/13/20 5:52 AM, Kirill A. Shutemov wrote:
> __collapse_huge_page_isolate() may fail due to extra pin in the LRU add
> pagevec. It's pretty common for swapin case: we swap in pages just to
> fail due to the extra pin.
>
> Drain LRU add pagevec on successful swapin.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> ---
>   mm/khugepaged.c | 5 +++++
>   1 file changed, 5 insertions(+)

Acked-by: Yang Shi <yang.shi@linux.alibaba.com>

>
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index ee66c140c2d6..e3e41c2768d8 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -934,6 +934,11 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm,
>   	}
>   	vmf.pte--;
>   	pte_unmap(vmf.pte);
> +
> +	/* Drain LRU add pagevec to remove extra pin on the swapped in pages */
> +	if (swapped_in)
> +		lru_add_drain();
> +
>   	trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1);
>   	return true;
>   }