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Subject: Re: ZONE_DMA (was: Re: 2.6.19 -mm merge plans)
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
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Date: Thu, 21 Sep 2006 02:03:50 +0100
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To: Christoph Lameter <clameter@sgi.com>
Cc: Andrew Morton <akpm@osdl.org>, "Martin J. Bligh" <mbligh@mbligh.org>, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, Christoph Hellwig <hch@infradead.org>
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Ar Mer, 2006-09-20 am 17:31 -0700, ysgrifennodd Christoph Lameter:
> ZONE_DMA does not have a bright future with IOMMUs and other things 
> around. None of my system uses ZONE_DMA and I have a variety of them.

IOMMUs don't always help. They IOMMU aperture on AMD64 for example is
too high to help devices with below 32bit limits.