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    SubjectRe: [patch] x86: allow ZONE_DMA to be configurable
    On Wed, 13 Oct 2010 17:15:04 -0700 (PDT) David Rientjes <> wrote:

    > ZONE_DMA is unnecessary for a large number of machines that do not
    > require addressing in the lower 16MB of memory because they do not use
    > ISA devices with 16-bit address registers (plus one page byte register).
    > This patch allows users to disable ZONE_DMA for x86 if they know they
    > will not be using such devices with their kernel.
    > This prevents the VM from unnecessarily reserving a ratio of memory
    > (defaulting to 1/256th of system capacity) with lowmem_reserve_ratio
    > for such allocations when it will never be used.

    I wonder how hard it would be to do this at runtime, probably with a
    boot parameter.

    I'd be a little concerned at the effects of this on page reclaim and
    the page allocator - it might expose weird pre-existing bugs or
    inefficiencies. But we can cross that bridge when we fall off it, I

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