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    SubjectRe: [tip:x86/mm] x86, mm: Allow ZONE_DMA to be configurable
    On Mon, May 16, 2011 at 11:13:07PM +0000, tip-bot for David Rientjes wrote:
    > Commit-ID: dc382fd5bcca7098a984705ed6ac880f539d068e
    > Gitweb: http://git.kernel.org/tip/dc382fd5bcca7098a984705ed6ac880f539d068e
    > Author: David Rientjes <rientjes@google.com>
    > AuthorDate: Mon, 16 May 2011 13:54:10 -0700
    > Committer: H. Peter Anvin <hpa@linux.intel.com>
    > CommitDate: Mon, 16 May 2011 14:03:28 -0700
    >
    > x86, mm: Allow ZONE_DMA to be configurable
    >
    > ZONE_DMA is unnecessary for a large number of machines that do not
    > require less than 32-bit DMA addressing, e.g. ISA legacy DMA or PCI
    > cards with a restricted DMA address mask.
    >
    > 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.
    >
    > Signed-off-by: David Rientjes <rientjes@google.com>
    > Link: http://lkml.kernel.org/r/alpine.DEB.2.00.1105161353560.4353@chino.kir.corp.google.com
    > Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

    This causes the ZONE_DMA menu option to appear in the toplevel menu of
    the kernel configurator instead of under EXPERT, where it should belong
    IMO.

    > ---
    > arch/x86/Kconfig | 9 ++++++++-
    > arch/x86/mm/init_32.c | 2 ++
    > arch/x86/mm/init_64.c | 2 ++
    > 3 files changed, 12 insertions(+), 1 deletions(-)
    >
    > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
    > index 648fca4..0eb801a 100644
    > --- a/arch/x86/Kconfig
    > +++ b/arch/x86/Kconfig
    > @@ -112,7 +112,14 @@ config MMU
    > def_bool y
    >
    > config ZONE_DMA
    > - def_bool y
    > + bool "DMA memory allocation support" if EXPERT
    > + default y
    > + help
    > + DMA memory allocation support allows devices with less than 32-bit
    > + addressing to allocate within the first 16MB of address space.
    > + Disable if no such devices will be used.
    > +
    > + If unsure, say Y.

    maybe this should go into init/Kconfig ?

    Thanks.

    --
    Regards/Gruss,
    Boris.

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