From: Eric Dumazet <edumazet@google.com>
Date: Mon, 15 Nov 2021 19:02:30 +0000 (-0800)
Subject: tcp: minor optimization in tcp_add_backlog()
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=d519f350967a60b85a574ad8aeac43f2b4384746;p=linux.git

tcp: minor optimization in tcp_add_backlog()

If packet is going to be coalesced, sk_sndbuf/sk_rcvbuf values
are not used. Defer their access to the point we need them.

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

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 13d868c432845..82a9e1b75405f 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1800,8 +1800,7 @@ int tcp_v4_early_demux(struct sk_buff *skb)
 
 bool tcp_add_backlog(struct sock *sk, struct sk_buff *skb)
 {
-	u32 limit = READ_ONCE(sk->sk_rcvbuf) + READ_ONCE(sk->sk_sndbuf);
-	u32 tail_gso_size, tail_gso_segs;
+	u32 limit, tail_gso_size, tail_gso_segs;
 	struct skb_shared_info *shinfo;
 	const struct tcphdr *th;
 	struct tcphdr *thtail;
@@ -1909,7 +1908,7 @@ no_coalesce:
 	 * to reduce memory overhead, so add a little headroom here.
 	 * Few sockets backlog are possibly concurrently non empty.
 	 */
-	limit += 64*1024;
+	limit = READ_ONCE(sk->sk_rcvbuf) + READ_ONCE(sk->sk_sndbuf) + 64*1024;
 
 	if (unlikely(sk_add_backlog(sk, skb, limit))) {
 		bh_unlock_sock(sk);