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    From
    SubjectRe: Is sendfile all that sexy?
    Date
    In article <200101192018.XAA25263@ms2.inr.ac.ru>,
    <kuznet@ms2.inr.ac.ru> wrote:
    >Hello!
    >
    >> It's about direct i/o from/to pages,
    >
    >Yes. Formally, there are no problems to send to tcp directly from io space.

    Actually, as long as there is no "struct page" there _are_ problems.
    This is why the NUMA stuff was brought up - it would require that there
    be a mem_map for the PCI pages.. (to do ref-counting etc).

    >But could someone explain me one thing. Does bus-mastering
    >from io really work? And if it does, is it enough fast?
    >At least, looking at my book on pci, I do not understand
    >how such transfers are able to use bursts. MRM is banned for them...

    It does work at least on some hardware. But no, I don't think you can
    depend on bursting (but I don't see why it couldn't work in theory).

    Linus
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