tcp: hint compiler about sack flows

Eric Dumazet · davem330 · commit ebeef4bcccf4 · 2018-11-30T13:26:53.000-08:00
Tell the compiler that most TCP flows are using SACK these days.

There is no need to add the unlikely() clause in tcp_is_reno(),
the compiler is able to infer it.

Signed-off-by: Eric Dumazet &lt;edumazet@google.com&gt;
Acked-by: Neal Cardwell &lt;ncardwell@google.com&gt;
Acked-by: Yuchung Cheng &lt;ycheng@google.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
diff --git a/include/net/tcp.h b/include/net/tcp.h
@@ -1124,7 +1124,7 @@ void tcp_rate_check_app_limited(struct sock *sk);
  */
 static inline int tcp_is_sack(const struct tcp_sock *tp)
 {
-	return tp->rx_opt.sack_ok;
+	return likely(tp->rx_opt.sack_ok);
 }
 
 static inline bool tcp_is_reno(const struct tcp_sock *tp)

Original file line number	Diff line number	Diff line change
`@@ -1124,7 +1124,7 @@ void tcp_rate_check_app_limited(struct sock *sk);`
`1124`	`1124`	`*/`
`1125`	`1125`	`static inline int tcp_is_sack(const struct tcp_sock *tp)`
`1126`	`1126`	`{`
`1127`		`- return tp->rx_opt.sack_ok;`
	`1127`	`+ return likely(tp->rx_opt.sack_ok);`
`1128`	`1128`	`}`
`1129`	`1129`
`1130`	`1130`	`static inline bool tcp_is_reno(const struct tcp_sock *tp)`