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    SubjectRe: hackbench regression due to commit 9dfc6e68bfe6e
    From: David Miller <>
    Date: Thu, 08 Apr 2010 00:05:57 -0700 (PDT)

    > From: Eric Dumazet <>
    > Date: Thu, 08 Apr 2010 09:00:19 +0200
    >> If run individually, the tests results are more what we would expect
    >> (slow), but if machine runs the two set of process concurrently, each
    >> group runs much faster...
    > BTW, I just discovered (thanks to the function graph tracer, woo hoo!)
    > that loopback TCP packets get fully checksum validated on receive.
    > I'm trying to figure out why skb->ip_summed ends up being
    > CHECKSUM_NONE in tcp_v4_rcv() even though it gets set to
    > CHECKSUM_PARTIAL in tcp_sendmsg().

    Ok, it looks like it's only ACK packets that have this problem,
    but still :-)

    It's weird that we have a special ip_dev_loopback_xmit() for for
    ip_mc_output() NF_HOOK()s, which forces skb->ip_summed to
    CHECKSUM_UNNECESSARY, but the actual normal loopback xmit doesn't
    do that...

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      Last update: 2010-04-08 09:23    [from the cache]
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