From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Subject: Re: [PATCH 4/4] mm: vmscan: If kswapd has been running too long,
 allow it to sleep
Date: Wed, 18 May 2011 10:05:50 +0900
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> 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.