linux-kernel - Re: Free memory never fully used, swapping

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Date:	Wed,  1 Dec 2010 19:17:07 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Christoph Lameter <cl@...ux.com>
Cc:	kosaki.motohiro@...fujitsu.com, Simon Kirby <sim@...tway.ca>,
	Mel Gorman <mel@....ul.ie>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel <linux-kernel@...r.kernel.org>, linux-mm@...ck.org
Subject: Re: Free memory never fully used, swapping

> On Tue, 30 Nov 2010, KOSAKI Motohiro wrote:
> 
> > This?
> 
> Specifying a parameter to temporarily override to see if this has the
> effect is ok. But this has worked for years now. There must be something
> else going with with reclaim that causes these issues now.

I don't think this has worked. Simon have found the corner case recently,
but it is not new.

So I hope you realize that high order allocation is no free lunch. __GFP_NORETRY
makes no sense really. Even though we have compaction, high order reclaim is still
costly operation.

I don't think SLUB's high order allocation trying is bad idea. but now It 
does more costly trying. that's bad. Also I'm worry about SLUB assume too 
higher end machine. Now Both SLES and RHEL decided to don't use SLUB, 
instead use SLAB. Now linux community is fragmented. If you are still 
interesting SL*B unification, can you please consider to join corner 
case smashing activity?

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