Messages in this thread | | | Date | Thu, 08 Apr 2010 00:20:11 -0700 (PDT) | Subject | Re: hackbench regression due to commit 9dfc6e68bfe6e | From | David Miller <> |
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From: David Miller <davem@davemloft.net> Date: Thu, 08 Apr 2010 00:05:57 -0700 (PDT)
> From: Eric Dumazet <eric.dumazet@gmail.com> > 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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