netdev - [PATCH v2 net-next 2/8] net: move sk->sk_err_soft and sk->sk

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Message-ID: <20250919204856.2977245-3-edumazet@google.com>
Date: Fri, 19 Sep 2025 20:48:50 +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 2/8] net: move sk->sk_err_soft and sk->sk_sndbuf

sk->sk_sndbuf is read-mostly in tx path, so move it from
sock_write_tx group to more appropriate sock_read_tx.

sk->sk_err_soft was not identified previously, but
is used from tcp_ack().

Move it to sock_write_tx group for better cache locality.

Also change tcp_ack() to clear sk->sk_err_soft only if needed.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/net/sock.h   | 4 ++--
 net/core/sock.c      | 3 ++-
 net/ipv4/tcp_input.c | 3 ++-
 3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/include/net/sock.h b/include/net/sock.h
index 66c2f396b57de5a0048b4ae1e6181c4473be15c5..b4fefeea0213a548a1c3601b95f902a5fa499bc6 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -467,7 +467,7 @@ struct sock {
 	__cacheline_group_begin(sock_write_tx);
 	int			sk_write_pending;
 	atomic_t		sk_omem_alloc;
-	int			sk_sndbuf;
+	int			sk_err_soft;
 
 	int			sk_wmem_queued;
 	refcount_t		sk_wmem_alloc;
@@ -507,6 +507,7 @@ struct sock {
 	unsigned int		sk_gso_max_size;
 	gfp_t			sk_allocation;
 	u32			sk_txhash;
+	int			sk_sndbuf;
 	u8			sk_pacing_shift;
 	bool			sk_use_task_frag;
 	__cacheline_group_end(sock_read_tx);
@@ -523,7 +524,6 @@ struct sock {
 	unsigned long	        sk_lingertime;
 	struct proto		*sk_prot_creator;
 	rwlock_t		sk_callback_lock;
-	int			sk_err_soft;
 	u32			sk_ack_backlog;
 	u32			sk_max_ack_backlog;
 	unsigned long		sk_ino;
diff --git a/net/core/sock.c b/net/core/sock.c
index ad79efde447675c8a8a3aafe204e2bbb1a5efe7c..dc03d4b5909a2a68aee84eb9a153b2c3970f6b32 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -4452,7 +4452,7 @@ static int __init sock_struct_check(void)
 
 	CACHELINE_ASSERT_GROUP_MEMBER(struct sock, sock_write_tx, sk_omem_alloc);
 	CACHELINE_ASSERT_GROUP_MEMBER(struct sock, sock_write_tx, sk_omem_alloc);
-	CACHELINE_ASSERT_GROUP_MEMBER(struct sock, sock_write_tx, sk_sndbuf);
+	CACHELINE_ASSERT_GROUP_MEMBER(struct sock, sock_write_tx, sk_err_soft);
 	CACHELINE_ASSERT_GROUP_MEMBER(struct sock, sock_write_tx, sk_wmem_queued);
 	CACHELINE_ASSERT_GROUP_MEMBER(struct sock, sock_write_tx, sk_wmem_alloc);
 	CACHELINE_ASSERT_GROUP_MEMBER(struct sock, sock_write_tx, sk_tsq_flags);
@@ -4479,6 +4479,7 @@ static int __init sock_struct_check(void)
 	CACHELINE_ASSERT_GROUP_MEMBER(struct sock, sock_read_tx, sk_gso_max_size);
 	CACHELINE_ASSERT_GROUP_MEMBER(struct sock, sock_read_tx, sk_allocation);
 	CACHELINE_ASSERT_GROUP_MEMBER(struct sock, sock_read_tx, sk_txhash);
+	CACHELINE_ASSERT_GROUP_MEMBER(struct sock, sock_read_tx, sk_sndbuf);
 	CACHELINE_ASSERT_GROUP_MEMBER(struct sock, sock_read_tx, sk_gso_max_segs);
 	CACHELINE_ASSERT_GROUP_MEMBER(struct sock, sock_read_tx, sk_pacing_shift);
 	CACHELINE_ASSERT_GROUP_MEMBER(struct sock, sock_read_tx, sk_use_task_frag);
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 9fdc6ce25eb1035a88ff2640601cc665187a78b2..f93d48d98d5dacf2ee868cd6b2d65a396443d106 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4085,7 +4085,8 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
 	/* We passed data and got it acked, remove any soft error
 	 * log. Something worked...
 	 */
-	WRITE_ONCE(sk->sk_err_soft, 0);
+	if (READ_ONCE(sk->sk_err_soft))
+		WRITE_ONCE(sk->sk_err_soft, 0);
 	WRITE_ONCE(icsk->icsk_probes_out, 0);
 	tp->rcv_tstamp = tcp_jiffies32;
 	if (!prior_packets)
-- 
2.51.0.470.ga7dc726c21-goog