linux-kernel - Re: [PATCH] vmscan: bail out of page reclaim after swap_cluster

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Message-Id: <20081125203333.26F0.KOSAKI.MOTOHIRO@jp.fujitsu.com>
Date:	Tue, 25 Nov 2008 20:35:12 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Rik van Riel <riel@...hat.com>
Cc:	kosaki.motohiro@...fujitsu.com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, mel@....ul.ie,
	akpm@...ux-foundation.org
Subject: Re: [PATCH] vmscan: bail out of page reclaim after swap_cluster_max pages

> Sometimes the VM spends the first few priority rounds rotating back
> referenced pages and submitting IO.  Once we get to a lower priority,
> sometimes the VM ends up freeing way too many pages.
> 
> The fix is relatively simple: in shrink_zone() we can check how many
> pages we have already freed, direct reclaim tasks break out of the
> scanning loop if they have already freed enough pages and have reached
> a lower priority level.
> 
> However, in order to do this we do need to know how many pages we already
> freed, so move nr_reclaimed into scan_control.
> 
> Signed-off-by: Rik van Riel <riel@...hat.com>
> ---
> Kosaki, this should address the zone scanning pressure issue.

hmmmm. I still don't like the behavior when priority==DEF_PRIORITY.
but I also should explain by code and benchmark.

therefore, I'll try to mesure this patch in this week.

thanks.


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