netdev - [PATCH net-next 4/7] tcp: move recvmsg_inq to tcp_sock_read

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Message-ID: <20250918155532.751173-5-edumazet@google.com>
Date: Thu, 18 Sep 2025 15:55:29 +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 net-next 4/7] tcp: move recvmsg_inq to tcp_sock_read_txrx

Fill a hole in tcp_sock_read_txrx, instead of possibly wasting
a cache line.

Note that tcp_recvmsg_locked() is also reading tp->repair,
so this removes one cache line miss in tcp recvmsg().

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                                       | 4 ++--
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/Documentation/networking/net_cachelines/tcp_sock.rst b/Documentation/networking/net_cachelines/tcp_sock.rst
index 429df29fba8bc08bce519870e403815780a2182b..c2138619b995882663a06c2a388d5333d6fe54f0 100644
--- a/Documentation/networking/net_cachelines/tcp_sock.rst
+++ b/Documentation/networking/net_cachelines/tcp_sock.rst
@@ -57,7 +57,7 @@ u8:1                          is_sack_reneg                               read_m
 u8:2                          fastopen_client_fail
 u8:4                          nonagle                 read_write                              tcp_skb_entail,tcp_push_pending_frames
 u8:1                          thin_lto
-u8:1                          recvmsg_inq
+u8:1                          recvmsg_inq                                 read_mostly         tcp_recvmsg
 u8:1                          repair                  read_mostly                             tcp_write_xmit
 u8:1                          frto
 u8                            repair_queue
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 1e6c2ded22c985134bd48b7bf5fd464e01e2fd51..c1d7fce251d74be8c5912526637f44c97905e738 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -232,7 +232,8 @@ struct tcp_sock {
 		repair      : 1,
 		tcp_usec_ts : 1, /* TSval values in usec */
 		is_sack_reneg:1,    /* in recovery from loss with SACK reneg? */
-		is_cwnd_limited:1;/* forward progress limited by snd_cwnd? */
+		is_cwnd_limited:1,/* forward progress limited by snd_cwnd? */
+		recvmsg_inq : 1;/* Indicate # of bytes in queue upon recvmsg */
 	__cacheline_group_end(tcp_sock_read_txrx);
 
 	/* RX read-mostly hotpath cache lines */
@@ -252,7 +253,6 @@ struct tcp_sock {
 #if defined(CONFIG_TLS_DEVICE)
 	void (*tcp_clean_acked)(struct sock *sk, u32 acked_seq);
 #endif
-	u8	recvmsg_inq : 1;/* Indicate # of bytes in queue upon recvmsg */
 	__cacheline_group_end(tcp_sock_read_rx);
 
 	/* TX read-write hotpath cache lines */
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 24787d2b04aa3d442175df41e0f507ad60398120..1d8611ad4c88f164eb45a54e1f6b812b1d02637d 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -5123,9 +5123,9 @@ static void __init tcp_struct_check(void)
 	CACHELINE_ASSERT_GROUP_MEMBER(struct tcp_sock, tcp_sock_read_rx, snd_ssthresh);
 #if IS_ENABLED(CONFIG_TLS_DEVICE)
 	CACHELINE_ASSERT_GROUP_MEMBER(struct tcp_sock, tcp_sock_read_rx, tcp_clean_acked);
-	CACHELINE_ASSERT_GROUP_SIZE(struct tcp_sock, tcp_sock_read_rx, 73);
+	CACHELINE_ASSERT_GROUP_SIZE(struct tcp_sock, tcp_sock_read_rx, 72);
 #else
-	CACHELINE_ASSERT_GROUP_SIZE(struct tcp_sock, tcp_sock_read_rx, 65);
+	CACHELINE_ASSERT_GROUP_SIZE(struct tcp_sock, tcp_sock_read_rx, 64);
 #endif
 
 	/* TX read-write hotpath cache lines */
-- 
2.51.0.384.g4c02a37b29-goog