inet: move ipv6only in sock_common

When an UDP application switches from AF_INET to AF_INET6 sockets, we
have a small performance degradation for IPv4 communications because of
extra cache line misses to access ipv6only information.

This can also be noticed for TCP listeners, as ipv6_only_sock() is also
used from __inet_lookup_listener()->compute_score()

This is magnified when SO_REUSEPORT is used.

Move ipv6only into struct sock_common so that it is available at
no extra cost in lookups.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 10 insertions, 7 deletions

diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index b0f2452f1d58..5dc68c3ebcbd 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -194,7 +194,7 @@ struct ipv6_pinfo {
 	                        sndflow:1,
 				repflow:1,
 				pmtudisc:3,
-				ipv6only:1,
+				padding:1,	/* 1 bit hole */
 				srcprefs:3,	/* 001: prefer temporary address
 						 * 010: prefer public address
 						 * 100: prefer care-of address
@@ -273,8 +273,8 @@ static inline void inet_sk_copy_descendant(struct sock *sk_to,
 	__inet_sk_copy_descendant(sk_to, sk_from, ancestor_size);
 }
 
-#define __ipv6_only_sock(sk)	(inet6_sk(sk)->ipv6only)
-#define ipv6_only_sock(sk)	((sk)->sk_family == PF_INET6 && __ipv6_only_sock(sk))
+#define __ipv6_only_sock(sk)	(sk->sk_ipv6only)
+#define ipv6_only_sock(sk)	(__ipv6_only_sock(sk))
 #define ipv6_sk_rxinfo(sk)	((sk)->sk_family == PF_INET6 && \
 				 inet6_sk(sk)->rxopt.bits.rxinfo)
 
@@ -287,8 +287,8 @@ static inline const struct in6_addr *inet6_rcv_saddr(const struct sock *sk)
 
 static inline int inet_v6_ipv6only(const struct sock *sk)
 {
-	return likely(sk->sk_state != TCP_TIME_WAIT) ?
-		ipv6_only_sock(sk) : inet_twsk(sk)->tw_ipv6only;
+	/* ipv6only field is at same position for timewait and other sockets */
+	return ipv6_only_sock(sk);
 }
 #else
 #define __ipv6_only_sock(sk)	0
diff --git a/include/net/inet_timewait_sock.h b/include/net/inet_timewait_sock.h
index 61474ea02152..6c566034e26d 100644
--- a/include/net/inet_timewait_sock.h
+++ b/include/net/inet_timewait_sock.h
@@ -108,6 +108,7 @@ struct inet_timewait_sock {
 #define tw_family		__tw_common.skc_family
 #define tw_state		__tw_common.skc_state
 #define tw_reuse		__tw_common.skc_reuse
+#define tw_ipv6only		__tw_common.skc_ipv6only
 #define tw_bound_dev_if		__tw_common.skc_bound_dev_if
 #define tw_node			__tw_common.skc_nulls_node
 #define tw_bind_node		__tw_common.skc_bind_node
@@ -131,7 +132,7 @@ struct inet_timewait_sock {
 	__be16			tw_sport;
 	kmemcheck_bitfield_begin(flags);
 	/* And these are ours. */
-	unsigned int		tw_ipv6only     : 1,
+	unsigned int		tw_pad0		: 1,	/* 1 bit hole */
 				tw_transparent  : 1,
 				tw_flowlabel	: 20,
 				tw_pad		: 2,	/* 2 bits hole */
diff --git a/include/net/sock.h b/include/net/sock.h
index 173cae485de1..8d4c9473e7d7 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -181,7 +181,8 @@ struct sock_common {
 	unsigned short		skc_family;
 	volatile unsigned char	skc_state;
 	unsigned char		skc_reuse:4;
-	unsigned char		skc_reuseport:4;
+	unsigned char		skc_reuseport:1;
+	unsigned char		skc_ipv6only:1;
 	int			skc_bound_dev_if;
 	union {
 		struct hlist_node	skc_bind_node;
@@ -317,6 +318,7 @@ struct sock {
 #define sk_state		__sk_common.skc_state
 #define sk_reuse		__sk_common.skc_reuse
 #define sk_reuseport		__sk_common.skc_reuseport
+#define sk_ipv6only		__sk_common.skc_ipv6only
 #define sk_bound_dev_if		__sk_common.skc_bound_dev_if
 #define sk_bind_node		__sk_common.skc_bind_node
 #define sk_prot			__sk_common.skc_prot