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    SubjectRe: [PATCH 2/3] x86/hash: swap parameters of crc32_u32()
    On 02/24/2014 04:41 AM, Jan Beulich wrote:
    >>
    >> So I'm guessing this hash is deliberately using the CRC32 instruction
    >> "backwards", which would actually make sense: an actual CRC is actually
    >> a pretty poor hash due to linearity.
    >>

    OK, it really is even more confusing than that.

    It does seem like the crc32 instruction really *is* commutative, which
    isn't something I would personally have expected at all.

    Given that fact, I suspect the ordering in the DPDK is actually a bug,
    and that we should correct the ordering (which I would do at the call
    sites because it seems to make the code clearer) because it reduces the
    size of the loop by two instructions.

    I guess I should find out how to file a bug report against DPDK too...

    -hpa



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