linux-kernel - Re: [PATCH 2/7] vmscan: synchronous lumpy reclaim don't call congestion

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Date:	Thu, 5 Aug 2010 16:06:05 +0100
From:	Mel Gorman <mel@....ul.ie>
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>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Minchan Kim <minchan.kim@...il.com>,
	Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH 2/7] vmscan: synchronous lumpy reclaim don't call
	congestion_wait()

On Thu, Aug 05, 2010 at 03:13:03PM +0900, KOSAKI Motohiro wrote:
> congestion_wait() mean "waiting quueue congestion is cleared".
> That said, if the system have plenty dirty pages and flusher thread push
> new request to IO queue conteniously, IO queue are not cleared
> congestion status for long time. thus, congestion_wait(HZ/10) become
> almostly equivalent schedule_timeout(HZ/10).
> 
> However, synchronous lumpy reclaim donesn't need this
> congestion_wait() at all. shrink_page_list(PAGEOUT_IO_SYNC) are
> using wait_on_page_writeback() and it provide sufficient waiting.
> 
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>

Needs rebasing for mmotm but otherwise;

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

> ---
>  mm/vmscan.c |    1 -
>  1 files changed, 0 insertions(+), 1 deletions(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index cf51d62..1cdc3db 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1341,7 +1341,6 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
>  
>  	/* Check if we should syncronously wait for writeback */
>  	if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) {
> -		congestion_wait(BLK_RW_ASYNC, HZ/10);
>  		/*
>  		 * The attempt at page out may have made some
>  		 * of the pages active, mark them inactive again.
> -- 
> 1.6.5.2
> 
> 
> 

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