Merge branch 'tcp-provide-better-locality-for-retransmit-timer'

Eric Dumazet says:

====================
tcp: provide better locality for retransmit timer

TCP stack uses three timers per flow, currently spread this way:

- sk->sk_timer : keepalive timer
- icsk->icsk_retransmit_timer : retransmit timer
- icsk->icsk_delack_timer : delayed ack timer

This series moves the retransmit timer to sk->sk_timer location,
to increase data locality in TX paths.

keepalive timers are not often used, this change should be neutral for them.

After the series we have following fields:

- sk->tcp_retransmit_timer : retransmit timer, in sock_write_tx group
- icsk->icsk_delack_timer : delayed ack timer
- icsk->icsk_keepalive_timer : keepalive timer

Moving icsk_delack_timer in a beter location would also be welcomed.
====================

Link: https://patch.msgid.link/20251124175013.1473655-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 9 insertions, 4 deletions

diff --git a/include/net/sock.h b/include/net/sock.h
index 38d48cfe0741..02253c6a578b 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -305,6 +305,8 @@ struct sk_filter;
   *	@sk_txrehash: enable TX hash rethink
   *	@sk_filter: socket filtering instructions
   *	@sk_timer: sock cleanup timer
+  *	@tcp_retransmit_timer: tcp retransmit timer
+  *	@mptcp_retransmit_timer: mptcp retransmit timer
   *	@sk_stamp: time stamp of last packet received
   *	@sk_stamp_seq: lock for accessing sk_stamp on 32 bit architectures only
   *	@sk_tsflags: SO_TIMESTAMPING flags
@@ -481,11 +483,12 @@ struct sock {
 		struct rb_root	tcp_rtx_queue;
 	};
 	struct sk_buff_head	sk_write_queue;
-	u32			sk_dst_pending_confirm;
-	u32			sk_pacing_status; /* see enum sk_pacing */
 	struct page_frag	sk_frag;
-	struct timer_list	sk_timer;
-
+	union {
+		struct timer_list	sk_timer;
+		struct timer_list	tcp_retransmit_timer;
+		struct timer_list	mptcp_retransmit_timer;
+	};
 	unsigned long		sk_pacing_rate; /* bytes per second */
 	atomic_t		sk_zckey;
 	atomic_t		sk_tskey;
@@ -493,6 +496,8 @@ struct sock {
 	__cacheline_group_end(sock_write_tx);
 
 	__cacheline_group_begin(sock_read_tx);
+	u32			sk_dst_pending_confirm;
+	u32			sk_pacing_status; /* see enum sk_pacing */
 	unsigned long		sk_max_pacing_rate;
 	long			sk_sndtimeo;
 	u32			sk_priority;