linux-kernel - Re: [PATCH 3/7] vmscan: synchrounous lumpy reclaim use lock_page() instead trylock

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Message-ID: <20100805141706.GB2985@barrios-desktop>
Date:	Thu, 5 Aug 2010 23:17:06 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Mel Gorman <mel@....ul.ie>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH 3/7] vmscan: synchrounous lumpy reclaim use lock_page()
 instead trylock_page()

On Thu, Aug 05, 2010 at 03:13:39PM +0900, KOSAKI Motohiro wrote:
> When synchrounous lumpy reclaim, there is no reason to give up to
> reclaim pages even if page is locked. We use lock_page() instead
> trylock_page() in this case.
> 
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> ---
>  mm/vmscan.c |    4 +++-
>  1 files changed, 3 insertions(+), 1 deletions(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 1cdc3db..833b6ad 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -665,7 +665,9 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>  		page = lru_to_page(page_list);
>  		list_del(&page->lru);
>  
> -		if (!trylock_page(page))
> +		if (sync_writeback == PAGEOUT_IO_SYNC)
> +			lock_page(page);
> +		else if (!trylock_page(page))
>  			goto keep;
>  
>  		VM_BUG_ON(PageActive(page));
> -- 
> 1.6.5.2
> 
> 
> 

Hmm. We can make sure lumpy already doesn't select the page locked?
I mean below scenario. 

LRU head -> page A -> page B -> LRU tail

lock_page(page A)
some_function()
direct reclaim
select victim page B
enter lumpy mode 
select victim page A as well as page B
shrink_page_list
lock_page(page A)


-- 
Kind regards,
Minchan Kim
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