linux-kernel - Re: [PATCH 4/4] mm: vmscan: If kswapd has been running too long, allow it to sleep

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Date:	Wed, 18 May 2011 10:05:50 +0900
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	minchan.kim@...il.com
CC:	mgorman@...e.de, James.Bottomley@...senpartnership.com,
	akpm@...ux-foundation.org, colin.king@...onical.com,
	raghu.prabhu13@...il.com, jack@...e.cz, chris.mason@...cle.com,
	cl@...ux.com, penberg@...nel.org, riel@...hat.com,
	hannes@...xchg.org, linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	linux-ext4@...r.kernel.org
Subject: Re: [PATCH 4/4] mm: vmscan: If kswapd has been running too long,
 allow it to sleep

> It would be better to put cond_resched after balance_pgdat?
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 292582c..61c45d0 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -2753,6 +2753,7 @@ static int kswapd(void *p)
>                  if (!ret) {
>                          trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
>                          order = balance_pgdat(pgdat, order,&classzone_idx);
> +                       cond_resched();
>                  }
>          }
>          return 0;
>
>>>> While it appears unlikely, there are bad conditions which can result
>> in cond_resched() being avoided.

Every reclaim priority decreasing or every shrink_zone() calling makes more
fine grained preemption. I think.


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