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    SubjectRe: mm and DMA devices


    On Thu, 21 Oct 1999, Dan Hollis wrote:

    > On Thu, 21 Oct 1999 kernel@kvack.org wrote:
    > > memory lists (say 1 per bit of significance above 24 bits). Practically,
    > > I have to ask what the value in this is. Do you really need to allocate >
    > > 16 MB in the normal use of a bloody sound card?
    >
    > No, but you have to make sure memory below 16mb is available :}
    >
    > Or even for many PCI cards, below 1gb or 2gb.
    >
    > Itd be *very* embarassing to have 4gb of ram, 2gb used, and not be able to
    > use your PCI soundcard because it cant allocate ram below 1gb.

    Do the math. Right now, GFP_DMA memory is the last part of system memory
    to be allocated from. Unless GFP_ATOMIC allocations consume all of the
    freepages.min memory reserve (which, for starters, is unlikely -- plus
    GFP_ATOMIC allocations are typically short term allocations for network
    buffers), you will be able to get GFP_DMA memory. That's the entire
    point of the changes made to the allocator. They may have been subtle,
    but their impact should be enourmously positive.

    -ben


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