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| author | Eric Dumazet <eric.dumazet@gmail.com> | 2011-11-09 08:24:35 +0100 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2011-11-09 22:36:27 +0100 |
| commit | d826eb14ecef3574b6b3be55e5f4329f4a76fbf3 (patch) | |
| tree | e072ee768f065be430543709d48f08a36f4eed2d /net/ipv6/udp.c | |
| parent | ipv4: reduce percpu needs for icmpmsg mibs (diff) | |
| download | linux-d826eb14ecef3574b6b3be55e5f4329f4a76fbf3.tar.xz linux-d826eb14ecef3574b6b3be55e5f4329f4a76fbf3.zip | |
ipv4: PKTINFO doesnt need dst reference
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: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv6/udp.c')
| -rw-r--r-- | net/ipv6/udp.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c index 846f4757eb8d..b4a4a15fa96f 100644 --- a/net/ipv6/udp.c +++ b/net/ipv6/udp.c @@ -538,7 +538,9 @@ int udpv6_queue_rcv_skb(struct sock * sk, struct sk_buff *skb) goto drop; } - if ((rc = ip_queue_rcv_skb(sk, skb)) < 0) { + skb_dst_drop(skb); + rc = sock_queue_rcv_skb(sk, skb); + if (rc < 0) { /* Note that an ENOMEM error is charged twice */ if (rc == -ENOMEM) UDP6_INC_STATS_BH(sock_net(sk), |