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    SubjectRe: bigphysarea support in 2.2.19 and 2.4.0 kernels
    Date
    Jes Sorensen writes:
    > Albert D Cahalan <acahalan@cs.uml.edu> writes:

    [about using huge physical allocations for number crunching]

    >> 2. Programming a DMA controller with multiple addresses isn't
    >> as fast as programming it with one.
    >
    > LOL
    >
    > Consider that allocating the larger block of memory is going
    > to take a lot longer than it will take for the DMA engine to
    > read the scatter/gather table entries and fetch a new address
    > word now and then.

    Say it takes a whole minute to allocate the memory. It wouldn't
    of course, because you'd allocate memory at boot, but anyway...
    Then the app runs, using that memory, for a multi-hour surgery.
    The allocation happens once; the inter-node DMA transfers occur
    dozens or hundreds of times per second.
    -
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