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From: Johannes Weiner <hannes@cmpxchg.org>
To: "Huang, Ying" <ying.huang@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	"Kirill A. Shutemov" <kirill@shutemov.name>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH -mm -v10 3/3] mm, THP, swap: Enable THP swap optimization only if has compound map
Date: Tue, 25 Apr 2017 17:46:18 -0400	[thread overview]
Message-ID: <20170425214618.GB6841@cmpxchg.org> (raw)
In-Reply-To: <20170425125658.28684-4-ying.huang@intel.com>

On Tue, Apr 25, 2017 at 08:56:58PM +0800, Huang, Ying wrote:
> From: Huang Ying <ying.huang@intel.com>
> 
> If there is no compound map for a THP (Transparent Huge Page), it is
> possible that the map count of some sub-pages of the THP is 0.  So it
> is better to split the THP before swapping out. In this way, the
> sub-pages not mapped will be freed, and we can avoid the unnecessary
> swap out operations for these sub-pages.
> 
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Signed-off-by: "Huang, Ying" <ying.huang@intel.com>

Acked-by: Johannes Weiner <hannes@cmpxchg.org>

CC Kirill to double check the reasoning here

> ---
>  mm/swap_state.c | 16 +++++++++++++---
>  1 file changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/swap_state.c b/mm/swap_state.c
> index 006d91d8fc53..13f83c6bb1b4 100644
> --- a/mm/swap_state.c
> +++ b/mm/swap_state.c
> @@ -192,9 +192,19 @@ int add_to_swap(struct page *page, struct list_head *list)
>  	VM_BUG_ON_PAGE(!PageLocked(page), page);
>  	VM_BUG_ON_PAGE(!PageUptodate(page), page);
>  
> -	/* cannot split, skip it */
> -	if (PageTransHuge(page) && !can_split_huge_page(page, NULL))
> -		return 0;
> +	if (PageTransHuge(page)) {
> +		/* cannot split, skip it */
> +		if (!can_split_huge_page(page, NULL))
> +			return 0;
> +		/*
> +		 * Split pages without a PMD map right away. Chances
> +		 * are some or all of the tail pages can be freed
> +		 * without IO.
> +		 */
> +		if (!compound_mapcount(page) &&
> +		    split_huge_page_to_list(page, list))
> +			return 0;
> +	}
>  
>  retry:
>  	entry = get_swap_page(page);
> -- 
> 2.11.0

  reply	other threads:[~2017-04-25 21:46 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-25 12:56 [PATCH -mm -v10 0/3] THP swap: Delay splitting THP during swapping out Huang, Ying
2017-04-25 12:56 ` [PATCH -mm -v10 1/3] mm, THP, swap: Delay splitting THP during swap out Huang, Ying
2017-04-27  5:31   ` Minchan Kim
2017-04-27  7:12     ` Huang, Ying
2017-04-27 13:37       ` Johannes Weiner
2017-04-28  8:40       ` Minchan Kim
2017-04-28 12:21         ` Huang, Ying
2017-05-10  1:03           ` Minchan Kim
2017-05-01 10:44         ` Johannes Weiner
2017-05-01 23:53           ` Minchan Kim
2017-05-10 13:56             ` Johannes Weiner
2017-05-10 23:25               ` Minchan Kim
2017-05-11  0:50                 ` Huang, Ying
2017-05-11  4:31                   ` Minchan Kim
2017-05-12  2:21                   ` [PATCH 1/2] mm: swap: unify swap slot free functions to put_swap_page Minchan Kim
2017-05-12  2:21                     ` [PATCH 2/2] mm: swap: move anonymous THP split logic to vmscan Minchan Kim
2017-05-12 16:48                       ` Johannes Weiner
2017-05-12 16:47                     ` [PATCH 1/2] mm: swap: unify swap slot free functions to put_swap_page Johannes Weiner
2017-05-11  1:22                 ` [PATCH -mm -v10 1/3] mm, THP, swap: Delay splitting THP during swap out Minchan Kim
2017-05-11 10:40                   ` Johannes Weiner
2017-05-12  1:34                     ` Minchan Kim
2017-04-25 12:56 ` [PATCH -mm -v10 2/3] mm, THP, swap: Check whether THP can be split firstly Huang, Ying
2017-04-25 21:43   ` Johannes Weiner
2017-04-25 12:56 ` [PATCH -mm -v10 3/3] mm, THP, swap: Enable THP swap optimization only if has compound map Huang, Ying
2017-04-25 21:46   ` Johannes Weiner [this message]
2017-04-28 13:16     ` Kirill A. Shutemov

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