linux-kernel - Re: [PATCH 09/10] mm: vmscan: Check if kswapd should writepage once per priority

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Date:	Thu, 21 Mar 2013 17:58:37 +0100
From:	Michal Hocko <mhocko@...e.cz>
To:	Mel Gorman <mgorman@...e.de>
Cc:	Linux-MM <linux-mm@...ck.org>, Jiri Slaby <jslaby@...e.cz>,
	Valdis Kletnieks <Valdis.Kletnieks@...edu>,
	Rik van Riel <riel@...hat.com>,
	Zlatko Calusic <zcalusic@...sync.net>,
	Johannes Weiner <hannes@...xchg.org>,
	dormando <dormando@...ia.net>,
	Satoru Moriya <satoru.moriya@....com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 09/10] mm: vmscan: Check if kswapd should writepage once
 per priority

On Sun 17-03-13 13:04:15, Mel Gorman wrote:
> Currently kswapd checks if it should start writepage as it shrinks
> each zone without taking into consideration if the zone is balanced or
> not. This is not wrong as such but it does not make much sense either.
> This patch checks once per priority if kswapd should be writing pages.

Except it is not once per priority strictly speaking...  It doesn't make
any difference though.

> Signed-off-by: Mel Gorman <mgorman@...e.de>

Reviewed-by: Michal Hocko <mhocko@...e.cz>

> ---
>  mm/vmscan.c | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 84375b2..8c66e5a 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -2804,6 +2804,13 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
>  		}
>  
>  		/*
> +		 * If we're getting trouble reclaiming, start doing writepage
> +		 * even in laptop mode.
> +		 */
> +		if (sc.priority < DEF_PRIORITY - 2)
> +			sc.may_writepage = 1;
> +
> +		/*
>  		 * Now scan the zone in the dma->highmem direction, stopping
>  		 * at the last zone which needs scanning.
>  		 *
> @@ -2876,13 +2883,6 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
>  				nr_to_reclaim += sc.nr_to_reclaim;
>  			}
>  
> -			/*
> -			 * If we're getting trouble reclaiming, start doing
> -			 * writepage even in laptop mode.
> -			 */
> -			if (sc.priority < DEF_PRIORITY - 2)
> -				sc.may_writepage = 1;
> -
>  			if (zone->all_unreclaimable) {
>  				if (end_zone && end_zone == i)
>  					end_zone--;
> -- 
> 1.8.1.4
> 

-- 
Michal Hocko
SUSE Labs
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