Date: Tue, 16 Sep 2003 18:17:08 +0200
From: Stephan von Krawczynski <skraw@ithnet.com>
To: Timothy Miller <miller@techsource.com>
Cc: alan@lxorguk.ukuu.org.uk, marcelo.tosatti@cyclades.com.br,
       neilb@cse.unsw.edu.au, linux-kernel@vger.kernel.org
Subject: Re: experiences beyond 4 GB RAM with 2.4.22
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On Tue, 16 Sep 2003 11:49:10 -0400
Timothy Miller <miller@techsource.com> wrote:

> Alan Cox wrote:
> > The kernel has no idea what you will do with given ram. It does try to
> > make some guesses but you are basically trying to paper over hardware
> > limits.
> 
> 
> Maybe not what you WILL DO, but what you HAVE DONE.  Those tasks which 
> have done the most DMA-requiring I/O could get preference for low 
> memory.  No?
> 
> Yeah, I know.. show you the code.  :)

That really sounds complex and therefore I would not try that in first place.
And it does not sound like a solution to my special problem of few tasks
operating on a lot of data (a lot more than fits to physical mem). For this
type of situation it would be really intelligent not to give away non-dma-able
memory. How can the kernel do that?
At least it knows that there are I/O devices that cannot cope with the mem it
is presenting. This sounds in fact simple.
The problem is: what _can_ be done with this type of mem at all?
It does not even help a lot if there are other devices that can handle it,
because you still must face the fact of a simple file-copy from such a capable
device to one that is not.
No wonder that the gurus did not have any good idea yet ;-)

Regards,
Stephan
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