linux-kernel - Re: [PATCH] prevent to reclaim anon page of lumpy reclaim for no swap space

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Date:	Thu, 25 Jun 2009 10:09:38 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Minchan Kim <minchan.kim@...il.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	linux-mm <linux-mm@...ck.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] prevent to reclaim anon page of lumpy reclaim for no
 swap space

Minchan Kim wrote:
> This patch prevent to reclaim anon page in case of no swap space.
> VM already prevent to reclaim anon page in various place.
> But it doesnt't prevent it for lumpy reclaim.
> 
> It shuffles lru list unnecessary so that it is pointless.
> Signed-off-by: Minchan Kim <minchan.kim@...il.com>
> ---
>  mm/vmscan.c |    6 ++++++
>  1 files changed, 6 insertions(+), 0 deletions(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 026f452..fb401fe 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -830,7 +830,13 @@ int __isolate_lru_page(struct page *page, int mode, int file)
>  	 * When this function is being called for lumpy reclaim, we
>  	 * initially look into all LRU pages, active, inactive and
>  	 * unevictable; only give shrink_page_list evictable pages.
> +
> +	 * If we don't have enough swap space, reclaiming of anon page
> +	 * is pointless.
>  	 */
> +	if (nr_swap_pages <= 0 && PageAnon(page))
> +		return ret;
> +

Should that be something like this:

	if (nr_swap_pages <= 0 && (PageAnon(page) && !PageSwapCache(page)))

We can still reclaim anonymous pages that already have
a swap slot assigned to them.

-- 
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