netdev - [PATCH v2 net-next 4/8] tcp: move tcp->rcv_tstamp to tcp_sock_write

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Message-ID: <20250919204856.2977245-5-edumazet@google.com>
Date: Fri, 19 Sep 2025 20:48:52 +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>, 
	Willem de Bruijn <willemb@...gle.com>, Kuniyuki Iwashima <kuniyu@...gle.com>, netdev@...r.kernel.org, 
	eric.dumazet@...il.com, Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH v2 net-next 4/8] tcp: move tcp->rcv_tstamp to
 tcp_sock_write_txrx group

tcp_ack() writes this field, it belongs to tcp_sock_write_txrx.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 Documentation/networking/net_cachelines/tcp_sock.rst | 2 +-
 include/linux/tcp.h                                  | 4 ++--
 net/ipv4/tcp.c                                       | 2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/Documentation/networking/net_cachelines/tcp_sock.rst b/Documentation/networking/net_cachelines/tcp_sock.rst
index d4dc018009451261c81a46dac2d6322005901c99..429df29fba8bc08bce519870e403815780a2182b 100644
--- a/Documentation/networking/net_cachelines/tcp_sock.rst
+++ b/Documentation/networking/net_cachelines/tcp_sock.rst
@@ -26,7 +26,7 @@ u64                           bytes_acked                                 read_w
 u32                           dsack_dups
 u32                           snd_una                 read_mostly         read_write          tcp_wnd_end,tcp_urg_mode,tcp_minshall_check,tcp_cwnd_validate(tx);tcp_ack,tcp_may_update_window,tcp_clean_rtx_queue(write),tcp_ack_tstamp(rx)
 u32                           snd_sml                 read_write                              tcp_minshall_check,tcp_minshall_update
-u32                           rcv_tstamp                                  read_mostly         tcp_ack
+u32                           rcv_tstamp              read_write          read_write          tcp_ack
 void *                        tcp_clean_acked                             read_mostly         tcp_ack
 u32                           lsndtime                read_write                              tcp_slow_start_after_idle_check,tcp_event_data_sent
 u32                           last_oow_ack_time
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 3ca5ed02de6d48e64c26744f117d72675f84a3f3..1e6c2ded22c985134bd48b7bf5fd464e01e2fd51 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -238,7 +238,6 @@ struct tcp_sock {
 	/* RX read-mostly hotpath cache lines */
 	__cacheline_group_begin(tcp_sock_read_rx);
 	u32	copied_seq;	/* Head of yet unread data */
-	u32	rcv_tstamp;	/* timestamp of last received ACK (for keepalives) */
 	u32	snd_wl1;	/* Sequence for window update		*/
 	u32	tlp_high_seq;	/* snd_nxt at the time of TLP */
 	u32	rttvar_us;	/* smoothed mdev_max			*/
@@ -246,13 +245,13 @@ struct tcp_sock {
 	u16	advmss;		/* Advertised MSS			*/
 	u16	urg_data;	/* Saved octet of OOB data and control flags */
 	u32	lost;		/* Total data packets lost incl. rexmits */
+	u32	snd_ssthresh;	/* Slow start size threshold		*/
 	struct  minmax rtt_min;
 	/* OOO segments go in this rbtree. Socket lock must be held. */
 	struct rb_root	out_of_order_queue;
 #if defined(CONFIG_TLS_DEVICE)
 	void (*tcp_clean_acked)(struct sock *sk, u32 acked_seq);
 #endif
-	u32	snd_ssthresh;	/* Slow start size threshold		*/
 	u8	recvmsg_inq : 1;/* Indicate # of bytes in queue upon recvmsg */
 	__cacheline_group_end(tcp_sock_read_rx);
 
@@ -319,6 +318,7 @@ struct tcp_sock {
 					*/
 	u32	app_limited;	/* limited until "delivered" reaches this val */
 	u32	rcv_wnd;	/* Current receiver window		*/
+	u32	rcv_tstamp;	/* timestamp of last received ACK (for keepalives) */
 /*
  *      Options received (usually on last packet, some only on SYN packets).
  */
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 5932dba3bd717b59e730630d7390b65f329b03c2..721287ca3328eb543e1d8c999b08ca617b77b8a7 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -5114,7 +5114,6 @@ static void __init tcp_struct_check(void)
 
 	/* RX read-mostly hotpath cache lines */
 	CACHELINE_ASSERT_GROUP_MEMBER(struct tcp_sock, tcp_sock_read_rx, copied_seq);
-	CACHELINE_ASSERT_GROUP_MEMBER(struct tcp_sock, tcp_sock_read_rx, rcv_tstamp);
 	CACHELINE_ASSERT_GROUP_MEMBER(struct tcp_sock, tcp_sock_read_rx, snd_wl1);
 	CACHELINE_ASSERT_GROUP_MEMBER(struct tcp_sock, tcp_sock_read_rx, tlp_high_seq);
 	CACHELINE_ASSERT_GROUP_MEMBER(struct tcp_sock, tcp_sock_read_rx, rttvar_us);
@@ -5164,6 +5163,7 @@ static void __init tcp_struct_check(void)
 	CACHELINE_ASSERT_GROUP_MEMBER(struct tcp_sock, tcp_sock_write_txrx, received_ecn_bytes);
 	CACHELINE_ASSERT_GROUP_MEMBER(struct tcp_sock, tcp_sock_write_txrx, app_limited);
 	CACHELINE_ASSERT_GROUP_MEMBER(struct tcp_sock, tcp_sock_write_txrx, rcv_wnd);
+	CACHELINE_ASSERT_GROUP_MEMBER(struct tcp_sock, tcp_sock_write_txrx, rcv_tstamp);
 	CACHELINE_ASSERT_GROUP_MEMBER(struct tcp_sock, tcp_sock_write_txrx, rx_opt);
 
 	/* RX read-write hotpath cache lines */
-- 
2.51.0.470.ga7dc726c21-goog