linux-kernel - Re: Deadlock possibly caused by too_many

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Date:	Tue, 19 Oct 2010 11:37:00 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Wu Fengguang <fengguang.wu@...el.com>
Cc:	kosaki.motohiro@...fujitsu.com,
	Andrew Morton <akpm@...ux-foundation.org>,
	Neil Brown <neilb@...e.de>, Rik van Riel <riel@...hat.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"Li, Shaohua" <shaohua.li@...el.com>
Subject: Re: Deadlock possibly caused by too_many_isolated.

> ---
> Subject: vmscan: comment too_many_isolated()
> From: Wu Fengguang <fengguang.wu@...el.com>
> Date: Tue Oct 19 09:53:23 CST 2010
> 
> Comment "Why it's doing so" rather than "What it does"
> as proposed by Andrew Morton.
> 
> Signed-off-by: Wu Fengguang <fengguang.wu@...el.com>
> ---
>  mm/vmscan.c |    6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> --- linux-next.orig/mm/vmscan.c	2010-10-19 09:29:44.000000000 +0800
> +++ linux-next/mm/vmscan.c	2010-10-19 10:21:41.000000000 +0800
> @@ -1142,7 +1142,11 @@ int isolate_lru_page(struct page *page)
>  }
>  
>  /*
> - * Are there way too many processes in the direct reclaim path already?
> + * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and
> + * then get resheduled. When there are massive number of tasks doing page
> + * allocation, such sleeping direct reclaimers may keep piling up on each CPU,
> + * the LRU list will go small and be scanned faster than necessary, leading to
> + * unnecessary swapping, thrashing and OOM.
>   */
>  static int too_many_isolated(struct zone *zone, int file,
>  		struct scan_control *sc)

nice!
	Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>


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