linux-kernel - Re: [PATCH v2] MM: handle THP in swap_*page_fs()

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Date:   Mon, 9 May 2022 16:54:50 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     NeilBrown <neilb@...e.de>,
        Andrew Morton <akpm@...ux-foundation.org>
CC:     Geert Uytterhoeven <geert+renesas@...der.be>,
        Christoph Hellwig <hch@....de>, <linux-nfs@...r.kernel.org>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH v2] MM: handle THP in swap_*page_fs() - count_vm_events()

On 2022/5/2 13:31, NeilBrown wrote:
> 
> We need to use count_swpout_vm_event() for sio_write_complete() to get
> correct counting.
> 
> Note that THP swap in (if it ever happens) is current accounted 1 for
> each page, whether HUGE or normal.  This is different from swap-out
> accounting.

Agree, there is no THP swap-in now.

> 
> This patch should be squashed into
>     MM: handle THP in swap_*page_fs()
> 

This patch looks good to me. Thanks!

Reviewed-by: Miaohe Lin <linmiaohe@...wei.com>

> Reported-by: Miaohe Lin <linmiaohe@...wei.com>
> Signed-off-by: NeilBrown <neilb@...e.de>
> ---
>  mm/page_io.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/page_io.c b/mm/page_io.c
> index d636a3531cad..1b8075ef3418 100644
> --- a/mm/page_io.c
> +++ b/mm/page_io.c
> @@ -280,8 +280,10 @@ static void sio_write_complete(struct kiocb *iocb, long ret)
>  			set_page_dirty(page);
>  			ClearPageReclaim(page);
>  		}
> -	} else
> -		count_vm_events(PSWPOUT, sio->pages);
> +	} else {
> +		for (p = 0; p < sio->pages; p++)
> +			count_swpout_vm_event(sio->bvec[p].bv_page);
> +	}
>  
>  	for (p = 0; p < sio->pages; p++)
>  		end_page_writeback(sio->bvec[p].bv_page);
>