linux-kernel - Re: [RFC 3/8] vmscan: make isolate_lru

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Date:	Thu, 28 Apr 2011 11:35:05 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Minchan Kim <minchan.kim@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-mm <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Christoph Lameter <cl@...ux.com>,
	Johannes Weiner <jweiner@...hat.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Rik van Riel <riel@...hat.com>,
	Andrea Arcangeli <aarcange@...hat.com>
Subject: Re: [RFC 3/8] vmscan: make isolate_lru_page with filter aware

On Wed, Apr 27, 2011 at 01:25:20AM +0900, Minchan Kim wrote:
> In some __zone_reclaim case, we don't want to shrink mapped page.
> Nonetheless, we have isolated mapped page and re-add it into
> LRU's head. It's unnecessary CPU overhead and makes LRU churning.
> 
> Of course, when we isolate the page, the page might be mapped but
> when we try to migrate the page, the page would be not mapped.
> So it could be migrated. But race is rare and although it happens,
> it's no big deal.
> 
> Cc: Christoph Lameter <cl@...ux.com>
> Cc: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> Cc: Mel Gorman <mgorman@...e.de>
> Cc: Rik van Riel <riel@...hat.com>
> Cc: Andrea Arcangeli <aarcange@...hat.com>
> Signed-off-by: Minchan Kim <minchan.kim@...il.com>

> index 71d2da9..e8d6190 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1147,7 +1147,8 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
>  
>  static unsigned long isolate_pages_global(unsigned long nr,
>  					struct list_head *dst,
> -					unsigned long *scanned, int order,
> +					unsigned long *scanned,
> +					struct scan_control *sc,
>  					int mode, struct zone *z,
>  					int active, int file)
>  {
> @@ -1156,8 +1157,8 @@ static unsigned long isolate_pages_global(unsigned long nr,
>  		lru += LRU_ACTIVE;
>  	if (file)
>  		lru += LRU_FILE;
> -	return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
> -					mode, file, 0, 0);
> +	return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, sc->order,
> +					mode, file, 0, !sc->may_unmap);
>  }
>  

Why not take may_writepage into account for dirty pages?

>  /*
> @@ -1407,7 +1408,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
>  
>  	if (scanning_global_lru(sc)) {
>  		nr_taken = isolate_pages_global(nr_to_scan,
> -			&page_list, &nr_scanned, sc->order,
> +			&page_list, &nr_scanned, sc,
>  			sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ?
>  					ISOLATE_BOTH : ISOLATE_INACTIVE,
>  			zone, 0, file);
> @@ -1531,7 +1532,7 @@ static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
>  	spin_lock_irq(&zone->lru_lock);
>  	if (scanning_global_lru(sc)) {
>  		nr_taken = isolate_pages_global(nr_pages, &l_hold,
> -						&pgscanned, sc->order,
> +						&pgscanned, sc,
>  						ISOLATE_ACTIVE, zone,
>  						1, file);
>  		zone->pages_scanned += pgscanned;
> -- 
> 1.7.1
> 

-- 
Mel Gorman
SUSE Labs
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