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    SubjectRe: PCI DMA to small buffers on cache-incoherent arch
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    >Remember please that specifically the DMA mapping APIs encourage use
    >of consistent memory for small data objects. It is specifically
    >because non-consistent DMA accesses to small bits are going to be very
    >slow (ie. the PCI controller is going to prefetch further cache lines
    >for no reason, for example). The non-consistent end of the APIs is
    >meant for long contiguous buffers, not small chunks.
    >
    >This is one of the reasons I want to fix this by making people use
    >either consistent memory or PCI pools (which is consistent memory
    >too).

    Please don't limit the API design to PCI ;)

    There are more and more embedded CPUs out there with their own
    bunch of on-chip devices that are neither consistent nor PCI based,
    their drivers will have the exact same problem to deal with though.

    Ben.

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