tcp/dccp: remove icsk->icsk_timeout

icsk->icsk_timeout can be replaced by icsk->icsk_retransmit_timer.expires

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

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250324203607.703850-2-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: edumazet

Documentation/networking/net_cachelines/inet_connection_sock.rst

@@ -12,8 +12,7 @@ struct inet_sock                    icsk_inet              read_mostly         r
 struct request_sock_queue           icsk_accept_queue
 struct inet_bind_bucket             icsk_bind_hash         read_mostly                             tcp_set_state
 struct inet_bind2_bucket            icsk_bind2_hash        read_mostly                             tcp_set_state,inet_put_port
-unsigned_long                       icsk_timeout           read_mostly                             inet_csk_reset_xmit_timer,tcp_connect
-struct timer_list                   icsk_retransmit_timer  read_mostly                             inet_csk_reset_xmit_timer,tcp_connect
+struct timer_list                   icsk_retransmit_timer  read_write                              inet_csk_reset_xmit_timer,tcp_connect
 struct timer_list                   icsk_delack_timer      read_mostly                             inet_csk_reset_xmit_timer,tcp_connect
 u32                                 icsk_rto               read_write                              tcp_cwnd_validate,tcp_schedule_loss_probe,tcp_connect_init,tcp_connect,tcp_write_xmit,tcp_push_one
 u32                                 icsk_rto_min

include/net/inet_connection_sock.h

@@ -56,7 +56,6 @@ struct inet_connection_sock_af_ops {
  * @icsk_accept_queue:	   FIFO of established children
  * @icsk_bind_hash:	   Bind node
  * @icsk_bind2_hash:	   Bind node in the bhash2 table
- * @icsk_timeout:	   Timeout
  * @icsk_retransmit_timer: Resend (no ack)
  * @icsk_rto:		   Retransmit timeout
  * @icsk_pmtu_cookie	   Last pmtu seen by socket
@@ -82,7 +81,6 @@ struct inet_connection_sock {
 	struct request_sock_queue icsk_accept_queue;
 	struct inet_bind_bucket	  *icsk_bind_hash;
 	struct inet_bind2_bucket  *icsk_bind2_hash;
-	unsigned long		  icsk_timeout;
  	struct timer_list	  icsk_retransmit_timer;
  	struct timer_list	  icsk_delack_timer;
 	__u32			  icsk_rto;
@@ -187,6 +185,12 @@ static inline void inet_csk_delack_init(struct sock *sk)
 	memset(&inet_csk(sk)->icsk_ack, 0, sizeof(inet_csk(sk)->icsk_ack));
 }
 
+static inline unsigned long
+icsk_timeout(const struct inet_connection_sock *icsk)
+{
+	return READ_ONCE(icsk->icsk_retransmit_timer.expires);
+}
+
 static inline void inet_csk_clear_xmit_timer(struct sock *sk, const int what)
 {
 	struct inet_connection_sock *icsk = inet_csk(sk);
@@ -225,8 +229,8 @@ static inline void inet_csk_reset_xmit_timer(struct sock *sk, const int what,
 	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);
-		icsk->icsk_timeout = jiffies + when;
-		sk_reset_timer(sk, &icsk->icsk_retransmit_timer, icsk->icsk_timeout);
+		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);

net/dccp/timer.c

@@ -139,9 +139,9 @@ static void dccp_write_timer(struct timer_list *t)
 	if (sk->sk_state == DCCP_CLOSED || !icsk->icsk_pending)
 		goto out;
 
-	if (time_after(icsk->icsk_timeout, jiffies)) {
+	if (time_after(icsk_timeout(icsk), jiffies)) {
 		sk_reset_timer(sk, &icsk->icsk_retransmit_timer,
-			       icsk->icsk_timeout);
+			       icsk_timeout(icsk));
 		goto out;
 	}
 

net/ipv4/inet_diag.c

@@ -315,12 +315,12 @@ int inet_sk_diag_fill(struct sock *sk, struct inet_connection_sock *icsk,
 		r->idiag_timer = 1;
 		r->idiag_retrans = icsk->icsk_retransmits;
 		r->idiag_expires =
-			jiffies_delta_to_msecs(icsk->icsk_timeout - jiffies);
+			jiffies_delta_to_msecs(icsk_timeout(icsk) - jiffies);
 	} else if (icsk_pending == ICSK_TIME_PROBE0) {
 		r->idiag_timer = 4;
 		r->idiag_retrans = icsk->icsk_probes_out;
 		r->idiag_expires =
-			jiffies_delta_to_msecs(icsk->icsk_timeout - jiffies);
+			jiffies_delta_to_msecs(icsk_timeout(icsk) - jiffies);
 	} else if (timer_pending(&sk->sk_timer)) {
 		r->idiag_timer = 2;
 		r->idiag_retrans = icsk->icsk_probes_out;

net/ipv4/tcp_ipv4.c

@@ -2923,10 +2923,10 @@ static void get_tcp4_sock(struct sock *sk, struct seq_file *f, int i)
 	    icsk_pending == ICSK_TIME_REO_TIMEOUT ||
 	    icsk_pending == ICSK_TIME_LOSS_PROBE) {
 		timer_active	= 1;
-		timer_expires	= icsk->icsk_timeout;
+		timer_expires	= icsk_timeout(icsk);
 	} else if (icsk_pending == ICSK_TIME_PROBE0) {
 		timer_active	= 4;
-		timer_expires	= icsk->icsk_timeout;
+		timer_expires	= icsk_timeout(icsk);
 	} else if (timer_pending(&sk->sk_timer)) {
 		timer_active	= 2;
 		timer_expires	= sk->sk_timer.expires;

net/ipv4/tcp_timer.c

@@ -509,7 +509,7 @@ static bool tcp_rtx_probe0_timed_out(const struct sock *sk,
 	 * and tp->rcv_tstamp might very well have been written recently.
 	 * rcv_delta can thus be negative.
 	 */
-	rcv_delta = icsk->icsk_timeout - tp->rcv_tstamp;
+	rcv_delta = icsk_timeout(icsk) - tp->rcv_tstamp;
 	if (rcv_delta <= timeout)
 		return false;
 
@@ -685,7 +685,8 @@ out:;
 }
 
 /* Called with bottom-half processing disabled.
-   Called by tcp_write_timer() */
+ * Called by tcp_write_timer() and tcp_release_cb().
+ */
 void tcp_write_timer_handler(struct sock *sk)
 {
 	struct inet_connection_sock *icsk = inet_csk(sk);
@@ -695,11 +696,11 @@ void tcp_write_timer_handler(struct sock *sk)
 	    !icsk->icsk_pending)
 		return;
 
-	if (time_after(icsk->icsk_timeout, jiffies)) {
-		sk_reset_timer(sk, &icsk->icsk_retransmit_timer, icsk->icsk_timeout);
+	if (time_after(icsk_timeout(icsk), jiffies)) {
+		sk_reset_timer(sk, &icsk->icsk_retransmit_timer,
+			       icsk_timeout(icsk));
 		return;
 	}
-
 	tcp_mstamp_refresh(tcp_sk(sk));
 	event = icsk->icsk_pending;
 

net/ipv6/tcp_ipv6.c

@@ -2195,10 +2195,10 @@ static void get_tcp6_sock(struct seq_file *seq, struct sock *sp, int i)
 	    icsk_pending == ICSK_TIME_REO_TIMEOUT ||
 	    icsk_pending == ICSK_TIME_LOSS_PROBE) {
 		timer_active	= 1;
-		timer_expires	= icsk->icsk_timeout;
+		timer_expires	= icsk_timeout(icsk);
 	} else if (icsk_pending == ICSK_TIME_PROBE0) {
 		timer_active	= 4;
-		timer_expires	= icsk->icsk_timeout;
+		timer_expires	= icsk_timeout(icsk);
 	} else if (timer_pending(&sp->sk_timer)) {
 		timer_active	= 2;
 		timer_expires	= sp->sk_timer.expires;

net/mptcp/protocol.c

@@ -422,7 +422,7 @@ static long mptcp_timeout_from_subflow(const struct mptcp_subflow_context *subfl
 	const struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
 
 	return inet_csk(ssk)->icsk_pending && !subflow->stale_count ?
-	       inet_csk(ssk)->icsk_timeout - jiffies : 0;
+	       icsk_timeout(inet_csk(ssk)) - jiffies : 0;
 }
 
 static void mptcp_set_timeout(struct sock *sk)

tools/testing/selftests/bpf/progs/bpf_iter_tcp4.c

@@ -99,10 +99,10 @@ static int dump_tcp_sock(struct seq_file *seq, struct tcp_sock *tp,
 	    icsk->icsk_pending == ICSK_TIME_REO_TIMEOUT ||
 	    icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) {
 		timer_active = 1;
-		timer_expires = icsk->icsk_timeout;
+		timer_expires = icsk->icsk_retransmit_timer.expires;
 	} else if (icsk->icsk_pending == ICSK_TIME_PROBE0) {
 		timer_active = 4;
-		timer_expires = icsk->icsk_timeout;
+		timer_expires = icsk->icsk_retransmit_timer.expires;
 	} else if (timer_pending(&sp->sk_timer)) {
 		timer_active = 2;
 		timer_expires = sp->sk_timer.expires;

tools/testing/selftests/bpf/progs/bpf_iter_tcp6.c

@@ -99,10 +99,10 @@ static int dump_tcp6_sock(struct seq_file *seq, struct tcp6_sock *tp,
 	    icsk->icsk_pending == ICSK_TIME_REO_TIMEOUT ||
 	    icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) {
 		timer_active = 1;
-		timer_expires = icsk->icsk_timeout;
+		timer_expires = icsk->icsk_retransmit_timer.expires;
 	} else if (icsk->icsk_pending == ICSK_TIME_PROBE0) {
 		timer_active = 4;
-		timer_expires = icsk->icsk_timeout;
+		timer_expires = icsk->icsk_retransmit_timer.expires;
 	} else if (timer_pending(&sp->sk_timer)) {
 		timer_active = 2;
 		timer_expires = sp->sk_timer.expires;