tcp: move inet->rx_dst_ifindex to sk->sk_rx_dst_ifindex

Increase cache locality by moving rx_dst_ifindex next to sk->sk_rx_dst

This is part of an effort to reduce cache line misses in TCP fast path.

This removes one cache line miss in early demux.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/inet_sock.h

@@ -207,11 +207,10 @@ struct inet_sock {
 	__be32			inet_saddr;
 	__s16			uc_ttl;
 	__u16			cmsg_flags;
+	struct ip_options_rcu __rcu	*inet_opt;
 	__be16			inet_sport;
 	__u16			inet_id;
 
-	struct ip_options_rcu __rcu	*inet_opt;
-	int			rx_dst_ifindex;
 	__u8			tos;
 	__u8			min_ttl;
 	__u8			mc_ttl;

include/net/sock.h

@@ -259,6 +259,7 @@ struct bpf_local_storage;
   *	@sk_rcvbuf: size of receive buffer in bytes
   *	@sk_wq: sock wait queue and async head
   *	@sk_rx_dst: receive input route used by early demux
+  *	@sk_rx_dst_ifindex: ifindex for @sk_rx_dst
   *	@sk_dst_cache: destination cache
   *	@sk_dst_pending_confirm: need to confirm neighbour
   *	@sk_policy: flow policy
@@ -430,6 +431,8 @@ struct sock {
 	struct xfrm_policy __rcu *sk_policy[2];
 #endif
 	struct dst_entry	*sk_rx_dst;
+	int			sk_rx_dst_ifindex;
+
 	struct dst_entry __rcu	*sk_dst_cache;
 	atomic_t		sk_omem_alloc;
 	int			sk_sndbuf;

net/ipv4/tcp_ipv4.c

@@ -1703,7 +1703,7 @@ int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
 		sock_rps_save_rxhash(sk, skb);
 		sk_mark_napi_id(sk, skb);
 		if (dst) {
-			if (inet_sk(sk)->rx_dst_ifindex != skb->skb_iif ||
+			if (sk->sk_rx_dst_ifindex != skb->skb_iif ||
 			    !INDIRECT_CALL_1(dst->ops->check, ipv4_dst_check,
 					     dst, 0)) {
 				dst_release(dst);
@@ -1788,7 +1788,7 @@ int tcp_v4_early_demux(struct sk_buff *skb)
 			if (dst)
 				dst = dst_check(dst, 0);
 			if (dst &&
-			    inet_sk(sk)->rx_dst_ifindex == skb->skb_iif)
+			    sk->sk_rx_dst_ifindex == skb->skb_iif)
 				skb_dst_set_noref(skb, dst);
 		}
 	}
@@ -2195,7 +2195,7 @@ void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb)
 
 	if (dst && dst_hold_safe(dst)) {
 		sk->sk_rx_dst = dst;
-		inet_sk(sk)->rx_dst_ifindex = skb->skb_iif;
+		sk->sk_rx_dst_ifindex = skb->skb_iif;
 	}
 }
 EXPORT_SYMBOL(inet_sk_rx_dst_set);

net/ipv6/tcp_ipv6.c

@@ -108,7 +108,7 @@ static void inet6_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb)
 		const struct rt6_info *rt = (const struct rt6_info *)dst;
 
 		sk->sk_rx_dst = dst;
-		inet_sk(sk)->rx_dst_ifindex = skb->skb_iif;
+		sk->sk_rx_dst_ifindex = skb->skb_iif;
 		tcp_inet6_sk(sk)->rx_dst_cookie = rt6_get_cookie(rt);
 	}
 }
@@ -1509,7 +1509,7 @@ static int tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb)
 		sock_rps_save_rxhash(sk, skb);
 		sk_mark_napi_id(sk, skb);
 		if (dst) {
-			if (inet_sk(sk)->rx_dst_ifindex != skb->skb_iif ||
+			if (sk->sk_rx_dst_ifindex != skb->skb_iif ||
 			    INDIRECT_CALL_1(dst->ops->check, ip6_dst_check,
 					    dst, np->rx_dst_cookie) == NULL) {
 				dst_release(dst);
@@ -1874,7 +1874,7 @@ INDIRECT_CALLABLE_SCOPE void tcp_v6_early_demux(struct sk_buff *skb)
 			if (dst)
 				dst = dst_check(dst, tcp_inet6_sk(sk)->rx_dst_cookie);
 			if (dst &&
-			    inet_sk(sk)->rx_dst_ifindex == skb->skb_iif)
+			    sk->sk_rx_dst_ifindex == skb->skb_iif)
 				skb_dst_set_noref(skb, dst);
 		}
 	}