tcp/dccp: remove icsk->icsk_ack.timeout

icsk->icsk_ack.timeout can be replaced by icsk->csk_delack_timer.expires

This saves 8 bytes in TCP/DCCP sockets and helps for better cache locality.

Signed-off-by: Eric Dumazet <[email protected]>
Reviewed-by: Kuniyuki Iwashima <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: edumazet

Documentation/networking/net_cachelines/inet_connection_sock.rst

@@ -38,7 +38,6 @@ struct icsk_ack_u8                  quick                  read_write          w
 struct icsk_ack_u8                  pingpong
 struct icsk_ack_u8                  retry                  write_mostly        read_write          inet_csk_clear_xmit_timer,tcp_rearm_rto,tcp_event_new_data_sent,tcp_write_xmit,__tcp_send_ack,tcp_send_ack,
 struct icsk_ack_u8                  ato                    read_mostly         write_mostly        tcp_dec_quickack_mode,tcp_event_ack_sent,__tcp_transmit_skb,__tcp_send_ack,tcp_send_ack
-struct icsk_ack_unsigned_long       timeout                read_write          read_write          inet_csk_reset_xmit_timer,tcp_connect
 struct icsk_ack_u32                 lrcvtime               read_write                              tcp_finish_connect,tcp_connect,tcp_event_data_sent,__tcp_transmit_skb
 struct icsk_ack_u16                 rcv_mss                write_mostly        read_mostly         __tcp_select_window,__tcp_cleanup_rbuf,tcp_initialize_rcv_mss,tcp_connect_init
 struct icsk_mtup_int                search_high            read_write                              tcp_mtup_init,tcp_sync_mss,tcp_connect_init,tcp_mtu_check_reprobe,tcp_write_xmit

include/net/inet_connection_sock.h

@@ -113,7 +113,6 @@ struct inet_connection_sock {
 				  lrcv_flowlabel:20, /* last received ipv6 flowlabel	   */
 				  dst_quick_ack:1, /* cache dst RTAX_QUICKACK		   */
 				  unused:3;
-		unsigned long	  timeout;	 /* Currently scheduled timeout		   */
 		__u32		  lrcvtime;	 /* timestamp of last received data packet */
 		__u16		  last_seg_size; /* Size of last incoming segment	   */
 		__u16		  rcv_mss;	 /* MSS used for delayed ACK decisions	   */
@@ -191,6 +190,12 @@ icsk_timeout(const struct inet_connection_sock *icsk)
 	return READ_ONCE(icsk->icsk_retransmit_timer.expires);
 }
 
+static inline unsigned long
+icsk_delack_timeout(const struct inet_connection_sock *icsk)
+{
+	return READ_ONCE(icsk->icsk_delack_timer.expires);
+}
+
 static inline void inet_csk_clear_xmit_timer(struct sock *sk, const int what)
 {
 	struct inet_connection_sock *icsk = inet_csk(sk);
@@ -226,16 +231,15 @@ static inline void inet_csk_reset_xmit_timer(struct sock *sk, const int what,
 		when = max_when;
 	}
 
+	when += jiffies;
 	if (what == ICSK_TIME_RETRANS || what == ICSK_TIME_PROBE0 ||
 	    what == ICSK_TIME_LOSS_PROBE || what == ICSK_TIME_REO_TIMEOUT) {
 		smp_store_release(&icsk->icsk_pending, what);
-		when += jiffies;
 		sk_reset_timer(sk, &icsk->icsk_retransmit_timer, when);
 	} else if (what == ICSK_TIME_DACK) {
 		smp_store_release(&icsk->icsk_ack.pending,
 				  icsk->icsk_ack.pending | ICSK_ACK_TIMER);
-		icsk->icsk_ack.timeout = jiffies + when;
-		sk_reset_timer(sk, &icsk->icsk_delack_timer, icsk->icsk_ack.timeout);
+		sk_reset_timer(sk, &icsk->icsk_delack_timer, when);
 	} else {
 		pr_debug("inet_csk BUG: unknown timer value\n");
 	}

net/dccp/output.c

@@ -627,11 +627,10 @@ void dccp_send_delayed_ack(struct sock *sk)
 			return;
 		}
 
-		if (!time_before(timeout, icsk->icsk_ack.timeout))
-			timeout = icsk->icsk_ack.timeout;
+		if (!time_before(timeout, icsk_delack_timeout(icsk)))
+			timeout = icsk_delack_timeout(icsk);
 	}
 	icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
-	icsk->icsk_ack.timeout = timeout;
 	sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
 }
 #endif

net/dccp/timer.c

@@ -185,9 +185,9 @@ static void dccp_delack_timer(struct timer_list *t)
 	if (sk->sk_state == DCCP_CLOSED ||
 	    !(icsk->icsk_ack.pending & ICSK_ACK_TIMER))
 		goto out;
-	if (time_after(icsk->icsk_ack.timeout, jiffies)) {
+	if (time_after(icsk_delack_timeout(icsk), jiffies)) {
 		sk_reset_timer(sk, &icsk->icsk_delack_timer,
-			       icsk->icsk_ack.timeout);
+			       icsk_delack_timeout(icsk));
 		goto out;
 	}
 

net/ipv4/tcp_output.c

@@ -4225,17 +4225,16 @@ void tcp_send_delayed_ack(struct sock *sk)
 	/* Use new timeout only if there wasn't a older one earlier. */
 	if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
 		/* If delack timer is about to expire, send ACK now. */
-		if (time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
+		if (time_before_eq(icsk_delack_timeout(icsk), jiffies + (ato >> 2))) {
 			tcp_send_ack(sk);
 			return;
 		}
 
-		if (!time_before(timeout, icsk->icsk_ack.timeout))
-			timeout = icsk->icsk_ack.timeout;
+		if (!time_before(timeout, icsk_delack_timeout(icsk)))
+			timeout = icsk_delack_timeout(icsk);
 	}
 	smp_store_release(&icsk->icsk_ack.pending,
 			  icsk->icsk_ack.pending | ICSK_ACK_SCHED | ICSK_ACK_TIMER);
-	icsk->icsk_ack.timeout = timeout;
 	sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
 }
 

net/ipv4/tcp_timer.c

@@ -322,8 +322,9 @@ void tcp_delack_timer_handler(struct sock *sk)
 	if (!(icsk->icsk_ack.pending & ICSK_ACK_TIMER))
 		return;
 
-	if (time_after(icsk->icsk_ack.timeout, jiffies)) {
-		sk_reset_timer(sk, &icsk->icsk_delack_timer, icsk->icsk_ack.timeout);
+	if (time_after(icsk_delack_timeout(icsk), jiffies)) {
+		sk_reset_timer(sk, &icsk->icsk_delack_timer,
+			       icsk_delack_timeout(icsk));
 		return;
 	}
 	icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER;

net/mptcp/options.c

@@ -432,7 +432,6 @@ static void clear_3rdack_retransmission(struct sock *sk)
 	struct inet_connection_sock *icsk = inet_csk(sk);
 
 	sk_stop_timer(sk, &icsk->icsk_delack_timer);
-	icsk->icsk_ack.timeout = 0;
 	icsk->icsk_ack.ato = 0;
 	icsk->icsk_ack.pending &= ~(ICSK_ACK_SCHED | ICSK_ACK_TIMER);
 }

net/mptcp/protocol.c

@@ -3420,7 +3420,6 @@ static void schedule_3rdack_retransmission(struct sock *ssk)
 	WARN_ON_ONCE(icsk->icsk_ack.pending & ICSK_ACK_TIMER);
 	smp_store_release(&icsk->icsk_ack.pending,
 			  icsk->icsk_ack.pending | ICSK_ACK_SCHED | ICSK_ACK_TIMER);
-	icsk->icsk_ack.timeout = timeout;
 	sk_reset_timer(ssk, &icsk->icsk_delack_timer, timeout);
 }