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    SubjectRe: Kernel checksum routime (>=5)x86 optimization
    Kurt Garloff wrote:
    > By the way: Is it correct to use adcl in this piece of code???
    > Why do we want to add 1 instead of 1<<32 in case of overflow???

    Because that's how the TCP checksum works. It's very clever because it
    can be written in the same fast way on little-endian and big-endian
    machines, and adding 16 bits, 32 bits, 64 bits or even 128 bits at a
    time.

    May I direct you to the rfc1071 which is all about these things. I
    quote:

    "This simple checksum has a number of wonderful mathematical
    properties that may be exploited to speed its calculation, as we
    will now discuss."

    > That might be the reason, yes.
    > it might also be that only one load can be executed per cycle.

    That's not true on a Pentium if you pick non-conflicting addresses.
    Both instructions in a pair can read from cache.
    (I forget the precise rule for conflicting addresses).

    -- Jamie

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