1. 14 Nov, 2011 22 commits
  2. 13 Nov, 2011 13 commits
  3. 12 Nov, 2011 4 commits
  4. 09 Nov, 2011 1 commit
    • Eric Dumazet's avatar
      ipv4: PKTINFO doesnt need dst reference · d826eb14
      Eric Dumazet authored
      Le lundi 07 novembre 2011 à 15:33 +0100, Eric Dumazet a écrit :
      
      > At least, in recent kernels we dont change dst->refcnt in forwarding
      > patch (usinf NOREF skb->dst)
      >
      > One particular point is the atomic_inc(dst->refcnt) we have to perform
      > when queuing an UDP packet if socket asked PKTINFO stuff (for example a
      > typical DNS server has to setup this option)
      >
      > I have one patch somewhere that stores the information in skb->cb[] and
      > avoid the atomic_{inc|dec}(dst->refcnt).
      >
      
      OK I found it, I did some extra tests and believe its ready.
      
      [PATCH net-next] ipv4: IP_PKTINFO doesnt need dst reference
      
      When a socket uses IP_PKTINFO notifications, we currently force a dst
      reference for each received skb. Reader has to access dst to get needed
      information (rt_iif & rt_spec_dst) and must release dst reference.
      
      We also forced a dst reference if skb was put in socket backlog, even
      without IP_PKTINFO handling. This happens under stress/load.
      
      We can instead store the needed information in skb->cb[], so that only
      softirq handler really access dst, improving cache hit ratios.
      
      This removes two atomic operations per packet, and false sharing as
      well.
      
      On a benchmark using a mono threaded receiver (doing only recvmsg()
      calls), I can reach 720.000 pps instead of 570.000 pps.
      
      IP_PKTINFO is typically used by DNS servers, and any multihomed aware
      UDP application.
      Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      d826eb14