netdev - [PATCH net-next 3/3] tcp: move tcp_rack_advance() to tcp

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Message-ID: <20260127032147.3498272-4-edumazet@google.com>
Date: Tue, 27 Jan 2026 03:21:47 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: Simon Horman <horms@...nel.org>, Neal Cardwell <ncardwell@...gle.com>, 
	Kuniyuki Iwashima <kuniyu@...gle.com>, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 3/3] tcp: move tcp_rack_advance() to tcp_input.c

tcp_rack_advance() is called from tcp_ack() and tcp_sacktag_one().

Moving it to tcp_input.c allows the compiler to inline it and save
both space and cpu cycles in TCP fast path.

$ scripts/bloat-o-meter -t vmlinux.1 vmlinux.2
add/remove: 0/2 grow/shrink: 1/1 up/down: 98/-132 (-34)
Function                                     old     new   delta
tcp_ack                                     5741    5839     +98
tcp_sacktag_one                              407     395     -12
__pfx_tcp_rack_advance                        16       -     -16
tcp_rack_advance                             104       -    -104
Total: Before=22572680, After=22572646, chg -0.00%

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/net/tcp.h       |  2 --
 net/ipv4/tcp_input.c    | 32 ++++++++++++++++++++++++++++++++
 net/ipv4/tcp_recovery.c | 32 --------------------------------
 3 files changed, 32 insertions(+), 34 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index a4d9f263ea68..f1cf9e6730c8 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -2514,8 +2514,6 @@ void tcp_newreno_mark_lost(struct sock *sk, bool snd_una_advanced);
 extern s32 tcp_rack_skb_timeout(struct tcp_sock *tp, struct sk_buff *skb,
 				u32 reo_wnd);
 extern bool tcp_rack_mark_lost(struct sock *sk);
-extern void tcp_rack_advance(struct tcp_sock *tp, u8 sacked, u32 end_seq,
-			     u64 xmit_time);
 extern void tcp_rack_reo_timeout(struct sock *sk);
 
 /* tcp_plb.c */
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index d504a9a9b6ec..a2a872382fc0 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1558,6 +1558,38 @@ static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb,
 	return in_sack;
 }
 
+/* Record the most recently (re)sent time among the (s)acked packets
+ * This is "Step 3: Advance RACK.xmit_time and update RACK.RTT" from
+ * draft-cheng-tcpm-rack-00.txt
+ */
+static void tcp_rack_advance(struct tcp_sock *tp, u8 sacked,
+			     u32 end_seq, u64 xmit_time)
+{
+	u32 rtt_us;
+
+	rtt_us = tcp_stamp_us_delta(tp->tcp_mstamp, xmit_time);
+	if (rtt_us < tcp_min_rtt(tp) && (sacked & TCPCB_RETRANS)) {
+		/* If the sacked packet was retransmitted, it's ambiguous
+		 * whether the retransmission or the original (or the prior
+		 * retransmission) was sacked.
+		 *
+		 * If the original is lost, there is no ambiguity. Otherwise
+		 * we assume the original can be delayed up to aRTT + min_rtt.
+		 * the aRTT term is bounded by the fast recovery or timeout,
+		 * so it's at least one RTT (i.e., retransmission is at least
+		 * an RTT later).
+		 */
+		return;
+	}
+	tp->rack.advanced = 1;
+	tp->rack.rtt_us = rtt_us;
+	if (tcp_skb_sent_after(xmit_time, tp->rack.mstamp,
+			       end_seq, tp->rack.end_seq)) {
+		tp->rack.mstamp = xmit_time;
+		tp->rack.end_seq = end_seq;
+	}
+}
+
 /* Mark the given newly-SACKed range as such, adjusting counters and hints. */
 static u8 tcp_sacktag_one(struct sock *sk,
 			  struct tcp_sacktag_state *state, u8 sacked,
diff --git a/net/ipv4/tcp_recovery.c b/net/ipv4/tcp_recovery.c
index 40732b84771e..139646751073 100644
--- a/net/ipv4/tcp_recovery.c
+++ b/net/ipv4/tcp_recovery.c
@@ -111,38 +111,6 @@ bool tcp_rack_mark_lost(struct sock *sk)
 	return !!timeout;
 }
 
-/* Record the most recently (re)sent time among the (s)acked packets
- * This is "Step 3: Advance RACK.xmit_time and update RACK.RTT" from
- * draft-cheng-tcpm-rack-00.txt
- */
-void tcp_rack_advance(struct tcp_sock *tp, u8 sacked, u32 end_seq,
-		      u64 xmit_time)
-{
-	u32 rtt_us;
-
-	rtt_us = tcp_stamp_us_delta(tp->tcp_mstamp, xmit_time);
-	if (rtt_us < tcp_min_rtt(tp) && (sacked & TCPCB_RETRANS)) {
-		/* If the sacked packet was retransmitted, it's ambiguous
-		 * whether the retransmission or the original (or the prior
-		 * retransmission) was sacked.
-		 *
-		 * If the original is lost, there is no ambiguity. Otherwise
-		 * we assume the original can be delayed up to aRTT + min_rtt.
-		 * the aRTT term is bounded by the fast recovery or timeout,
-		 * so it's at least one RTT (i.e., retransmission is at least
-		 * an RTT later).
-		 */
-		return;
-	}
-	tp->rack.advanced = 1;
-	tp->rack.rtt_us = rtt_us;
-	if (tcp_skb_sent_after(xmit_time, tp->rack.mstamp,
-			       end_seq, tp->rack.end_seq)) {
-		tp->rack.mstamp = xmit_time;
-		tp->rack.end_seq = end_seq;
-	}
-}
-
 /* We have waited long enough to accommodate reordering. Mark the expired
  * packets lost and retransmit them.
  */
-- 
2.53.0.rc1.217.geba53bf80e-goog