linux-kernel - Re: [PATCH 1/3] remove wrong rotation at lumpy reclaim

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Date:	Thu, 11 Jun 2009 16:06:27 +0100
From:	Mel Gorman <mel@....ul.ie>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kosaki.motohiro@...fujitsu.com" <kosaki.motohiro@...fujitsu.com>,
	"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>,
	"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	apw@...onical.com, riel@...hat.com, minchan.kim@...il.com
Subject: Re: [PATCH 1/3] remove wrong rotation at lumpy reclaim

On Thu, Jun 11, 2009 at 05:00:18PM +0900, KAMEZAWA Hiroyuki wrote:
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> 
> At lumpy reclaim, a page failed to be taken by __isolate_lru_page() can
> be pushed back to "src" list by list_move(). But the page may not be from
> "src" list. And list_move() itself is unnecessary because the page is
> not on top of LRU. Then, leave it as it is if __isolate_lru_page() fails.
> 
> This patch doesn't change the logic as "we should exit loop or not" and
> just fixes buggy list_move().
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> ---
>  mm/vmscan.c |    9 +--------
>  1 file changed, 1 insertion(+), 8 deletions(-)
> 
> Index: lumpy-reclaim-trial/mm/vmscan.c
> ===================================================================
> --- lumpy-reclaim-trial.orig/mm/vmscan.c
> +++ lumpy-reclaim-trial/mm/vmscan.c
> @@ -936,18 +936,11 @@ static unsigned long isolate_lru_pages(u
>  			/* Check that we have not crossed a zone boundary. */
>  			if (unlikely(page_zone_id(cursor_page) != zone_id))
>  				continue;
> -			switch (__isolate_lru_page(cursor_page, mode, file)) {
> -			case 0:
> +			if (__isolate_lru_page(cursor_page, mode, file) == 0) {
>  				list_move(&cursor_page->lru, dst);
>  				nr_taken++;
>  				scan++;
>  				break;
> -
> -			case -EBUSY:
> -				/* else it is being freed elsewhere */
> -				list_move(&cursor_page->lru, src);
> -			default:
> -				break;	/* ! on LRU or wrong list */
>  			}
>  		}
>  	}
> 

At very minimum, this avoids an unnecessary reshuffling of the LRU lists
during lumpy reclaim. Thanks

Acked-by: Mel Gorman <mel@....ul.ie>

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab
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