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    SubjectRe: [RFC 0/8] Reduce MAX_NR_ZONES and remove useless zones.
    On Tue, 4 Jul 2006, Christoph Hellwig wrote:

    > On Mon, Jul 03, 2006 at 04:26:57PM -0700, Christoph Lameter wrote:
    > > > Which btw is utterly wrong. It should have a 4GB ZONE_DMA32 and everything
    > > > else in ZONE_NORMAL.
    > >
    > > So we want to change the definition of ZONE_DMA to refer to the first 16MB
    > > only? ZONE_DMA32 is always a 4GB border?
    > The definition of ZONE_DMA32 is to be te 32bit border. I think we should
    > implement it wherever possible but at least on all architectures that
    > maybe have non-iommu implementations. ZONE_DMA should be an arch-specific
    > low memory zone.

    I guess then we should drop ZONE_DMA (its a misnoner anyways since it
    seems to indicate that DMA is only possible in this zone). Instead use

    ZONE_ISA_DMA -> ISA DMA Area (16 MB boundary)
    ZONE_32BIT_DMA -> 32bit DMA area (well 900 MB on x86_64 but somewhere in that area)
    only used for 64 bit platforms with 32 bit devices.
    <and maybe define new ones in the future?>

    Some arches seem to make ZONE_DMA their default zone instead of
    ZONE_NORMAL if DMA is possible to all of memory. I think in that case we
    should have no ZONE_DMA at all.

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