From 447167bf565a474ff0cfb0f41d54936937479e97 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 11 Apr 2012 23:05:28 +0000 Subject: udp: intoduce udp_encap_needed static_key Most machines dont use UDP encapsulation (L2TP) Adds a static_key so that udp_queue_rcv_skb() doesnt have to perform a test if L2TP never setup the encap_rcv on a socket. Idea of this patch came after Simon Horman proposal to add a hook on TCP as well. If static_key is not yet enabled, the fast path does a single JMP . When static_key is enabled, JMP destination is patched to reach the real encap_type/encap_rcv logic, possibly adding cache misses. Signed-off-by: Eric Dumazet Cc: Simon Horman Cc: dev@openvswitch.org Signed-off-by: David S. Miller --- net/ipv4/udp.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) (limited to 'net/ipv4/udp.c') diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index fe141052a1b..ad1e0dd4da4 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -107,6 +107,7 @@ #include #include #include +#include #include "udp_impl.h" struct udp_table udp_table __read_mostly; @@ -1379,6 +1380,14 @@ static int __udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb) } +static struct static_key udp_encap_needed __read_mostly; +void udp_encap_enable(void) +{ + if (!static_key_enabled(&udp_encap_needed)) + static_key_slow_inc(&udp_encap_needed); +} +EXPORT_SYMBOL(udp_encap_enable); + /* returns: * -1: error * 0: success @@ -1400,7 +1409,7 @@ int udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb) goto drop; nf_reset(skb); - if (up->encap_type) { + if (static_key_false(&udp_encap_needed) && up->encap_type) { int (*encap_rcv)(struct sock *sk, struct sk_buff *skb); /* @@ -1760,6 +1769,7 @@ int udp_lib_setsockopt(struct sock *sk, int level, int optname, /* FALLTHROUGH */ case UDP_ENCAP_L2TPINUDP: up->encap_type = val; + udp_encap_enable(); break; default: err = -ENOPROTOOPT; -- cgit v1.2.3-18-g5258