linux-kernel - RE: Can Linux live without DMA zone?

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Message-Id: <1162451591.27131.2.camel@taijtu>
Date:	Thu, 02 Nov 2006 08:13:11 +0100
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Conke Hu <conke.hu@....com>
Cc:	Jun Sun <jsun@...sun.net>, linux-kernel@...r.kernel.org,
	Christoph Lameter <clameter@....com>
Subject: RE: Can Linux live without DMA zone?

On Thu, 2006-11-02 at 11:43 +0800, Conke Hu wrote:
> It seems a good idea.
> Is dma zone is still necessay on most modern computers?

(don't top post!)

if you would have used google, you'd have found this:
  http://www.mail-archive.com/linux-arch@vger.kernel.org/msg01623.html


cheers

> -----Original Message-----
> From: linux-kernel-owner@...r.kernel.org [mailto:linux-kernel-owner@...r.kernel.org] On Behalf Of Jun Sun
> Sent: 2006年11月2日 10:16
> To: linux-kernel@...r.kernel.org
> Subject: Can Linux live without DMA zone?
> 
> 
> I am trying to reserve a block of memory (>16MB) starting from 0 and hide it 
> from kernel.  A consequence is that DMA zone now has size 0.  That causes
> many drivers to grief (OOMs).
> 
> I see two ways out:
> 
> 1. Modify individual drivers and convince them not to alloc with GFP_DMA.
>    I have been trying to do this but do not seem to see an end of it.  :)
> 
> 2. Simply lie and increase MAX_DMA_ADDRESS to really big (like 1GB) so that
>    the whole memory region belongs to DMA zone.
> 
> #2 sounds pretty hackish.  I am sure something bad will happen
> sooner or later (like what?). But so far it appears to be working fine.
> 
> The fundamental question is: Has anybody tried to run Linux without 0 sized
> DMA zone before?  Am I doing something that nobody has done before (which is
> something really hard to believe these days with Linux :P)?
> 
> Cheers.
> 
> Jun
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