Date: Mon, 13 Feb 2006 13:16:00 -0800 (PST)
From: Christoph Lameter <clameter@engr.sgi.com>
To: David Lang <dlang@digitalinsight.com>
cc: Con Kolivas <kernel@kolivas.org>,
       linux kernel mailing list <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@osdl.org>, ck list <ck@vds.kolivas.org>
Subject: Re: [PATCH] mm: Implement Swap Prefetching v25
In-Reply-To: <Pine.LNX.4.62.0602131309120.2608@qynat.qvtvafvgr.pbz>
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References: <200602120141.46084.kernel@kolivas.org>
 <Pine.LNX.4.62.0602131256000.3026@schroedinger.engr.sgi.com>
 <Pine.LNX.4.62.0602131309120.2608@qynat.qvtvafvgr.pbz>
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On Mon, 13 Feb 2006, David Lang wrote:

> On Mon, 13 Feb 2006, Christoph Lameter wrote:
> > spare ram when swapping??? We are already under memory pressure. Why make
> > it worse by getting rid of the few bits of available memory? If a system
> > swaps then we are per definition in the bad performance range. Add more
> > memory.
> when a program exits it's memory is now free, rather then just waiting until
> something uses this memory up normally, this patch attempts to fill that
> memory with things that are expected to be useful (things that were swapped
> out)

Then trigger this action when a program exits and when you know there was 
enough freed up to justify such an action. However, this is still a 
heuristic. No one knows if the pages read from swap will be of any use at 
all. For all I know a process may want to allocate some memory and fail 
because the memory was needlessly spend to read in pages that no one 
needs.

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