linux-kernel - Re: [patch] memory reclaim more efficiently

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Message-Id: <20080623102854.37BE.KOSAKI.MOTOHIRO@jp.fujitsu.com>
Date:	Mon, 23 Jun 2008 10:49:10 +0900
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Takenori Nagano <t-nagano@...jp.nec.com>
Cc:	kosaki.motohiro@...fujitsu.com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Keiichi KII <kii@...ux.bs1.fc.nec.co.jp>
Subject: Re: [patch] memory reclaim more  efficiently

Hi nagano-san,

> In shrink_zone(), system can not return to user mode before it finishes to
> search LRU list. IMHO, it is very wasteful, since the user processes stay
> unnecessarily long time in shrink_zone() loop and application response time
> becomes relatively bad. This patch changes shrink_zone() that it finishes memory
> reclaim when it reclaims enough memory.
> 
> the conditions to end searching:
> 
> 1. order of request page is 0
> 2. process is not kswapd.
> 3. satisfy the condition to return try_to_free_pages()
>    # nr_reclaim > SWAP_CLUSTER_MAX

I have 3 question.

1. Do you have any performance number?
2. I think this patch advocate many try_to_free_pages() called is better than
   one try_to_free_page waste long time. right?
   and, why do you think so?
3. if this patch improve perfomance, I guess DEF_PRIORITY is
   too small on your machine.
   if DEF_PRIORITY is proportional to system memory, do your problem are solved?



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