linux-kernel - Re: [PATCH] vmscan: skip freeing memory from zones with lots free

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Date:	Sat, 29 Nov 2008 19:55:13 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	kosaki.motohiro@...fujitsu.com, Rik van Riel <riel@...hat.com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] vmscan: skip freeing memory from zones with lots free

> We already tried this, or something very similar in effect, I think...
> 
> 
> commit 26e4931632352e3c95a61edac22d12ebb72038fe
> Author: akpm <akpm>
> Date:   Sun Sep 8 19:21:55 2002 +0000
> 
>     [PATCH] refill the inactive list more quickly
>     
>     Fix a problem noticed by Ed Tomlinson: under shifting workloads the
>     shrink_zone() logic will refill the inactive load too slowly.
>     
>     Bale out of the zone scan when we've reclaimed enough pages.  Fixes a
>     rarely-occurring problem wherein refill_inactive_zone() ends up
>     shuffling 100,000 pages and generally goes silly.
>     
>     This needs to be revisited - we should go on and rebalance the lower
>     zones even if we reclaimed enough pages from highmem.
>     
> 
> 
> Then it was reverted a year or two later:
> 
> 
> commit 265b2b8cac1774f5f30c88e0ab8d0bcf794ef7b3
> Author: akpm <akpm>
> Date:   Fri Mar 12 16:23:50 2004 +0000
> 
>     [PATCH] vmscan: zone balancing fix
>     
>     We currently have a problem with the balancing of reclaim between zones: much
>     more reclaim happens against highmem than against lowmem.
>     
>     This patch partially fixes this by changing the direct reclaim path so it
>     does not bale out of the zone walk after having reclaimed sufficient pages
>     from highmem: go on to reclaim from lowmem regardless of how many pages we
>     reclaimed from lowmem.
>     
> 
> My changelog does not adequately explain the reasons.
> 
> But we don't want to rediscover these reasons in early 2010 :(  Some trolling
> of the linux-mm and lkml archives around those dates might help us avoid
> a mistake here.

I hope to digg past discussion archive.
Andrew, plese wait merge this patch awhile.



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