linux-kernel - Re: [PATCH v3 04/10] compaction: make isolate_lru

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Message-ID: <20110612144955.GC24323@tiehlicka.suse.cz>
Date:	Sun, 12 Jun 2011 16:49:55 +0200
From:	Michal Hocko <mhocko@...e.cz>
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>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Mel Gorman <mgorman@...e.de>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH v3 04/10] compaction: make isolate_lru_page with filter
 aware

On Tue 07-06-11 23:38:17, Minchan Kim wrote:
> In async mode, compaction doesn't migrate dirty or writeback pages.
> So, it's meaningless to pick the page and re-add it to lru list.
> 
> Of course, when we isolate the page in compaction, the page might
> be dirty or writeback but when we try to migrate the page, the page
> would be not dirty, writeback. So it could be migrated. But it's
> very unlikely as isolate and migration cycle is much faster than
> writeout.
> 
> So, this patch helps cpu and prevent unnecessary LRU churning.

I think you should introduce ISOLATE_CLEAN with this patch.
Apart from that it makes perfect sense. Feel free to add my
Reviewed-by: Michal Hocko <mhocko@...e.cz>

> 
> Cc: Andrea Arcangeli <aarcange@...hat.com>
> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> Acked-by: Johannes Weiner <hannes@...xchg.org>
> Acked-by: Mel Gorman <mgorman@...e.de>
> Acked-by: Rik van Riel <riel@...hat.com>
> Signed-off-by: Minchan Kim <minchan.kim@...il.com>
> ---
>  mm/compaction.c |    7 +++++--
>  1 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/compaction.c b/mm/compaction.c
> index f0d75e9..8079346 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -243,6 +243,7 @@ static unsigned long isolate_migratepages(struct zone *zone,
>  	unsigned long last_pageblock_nr = 0, pageblock_nr;
>  	unsigned long nr_scanned = 0, nr_isolated = 0;
>  	struct list_head *migratelist = &cc->migratepages;
> +	enum ISOLATE_MODE mode = ISOLATE_ACTIVE|ISOLATE_INACTIVE;
>  
>  	/* Do not scan outside zone boundaries */
>  	low_pfn = max(cc->migrate_pfn, zone->zone_start_pfn);
> @@ -326,9 +327,11 @@ static unsigned long isolate_migratepages(struct zone *zone,
>  			continue;
>  		}
>  
> +		if (!cc->sync)
> +			mode |= ISOLATE_CLEAN;
> + 
>  		/* Try isolate the page */
> -		if (__isolate_lru_page(page,
> -				ISOLATE_ACTIVE|ISOLATE_INACTIVE, 0) != 0)
> +		if (__isolate_lru_page(page, mode, 0) != 0)
>  			continue;
>  
>  		VM_BUG_ON(PageTransCompound(page));
> -- 
> 1.7.0.4
> 
> --
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-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic
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