[PATCH net-next] tcp: add tcp_mstamp_refresh_inline()

[PATCH net-next] tcp: add tcp_mstamp_refresh_inline()

[Eric Dumazet]

We want to inline tcp_mstamp_refresh() in fast path only:

- tcp_rcv_established()
- tcp_write_xmit()

Add tcp_mstamp_refresh_inline() for this purpose.

Add noinline qualifier on tcp_mstamp_refresh() for the other paths,
to reduce bloat.

$ scripts/bloat-o-meter -t vmlinux.old vmlinux.new
add/remove: 0/0 grow/shrink: 1/4 up/down: 26/-123 (-97)
Function                                     old     new   delta
tcp_rcv_established                         2238    2264     +26
tcp_connect                                 4027    4003     -24
tcp_tsq_write                                152     120     -32
tcp_send_active_reset                        476     444     -32
tcp_send_window_probe                        235     200     -35
Total: Before=25316710, After=25316613, chg -0.00%

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/net/tcp.h     | 10 ++++++++++
 net/ipv4/tcp_input.c  |  2 +-
 net/ipv4/tcp_output.c | 12 +++---------
 3 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index ecbadcb3a7446cb18c245e670ba49ff574dfaff7..fb2bc9edc7de01bfc494afa828428723a352c02b 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1015,6 +1015,16 @@ static inline u32 tcp_time_stamp_ts(const struct tcp_sock *tp)
 	return tcp_time_stamp_ms(tp);
 }
 
+/* Refresh clocks of a TCP socket,
+ * ensuring monotically increasing values.
+ */
+static inline void tcp_mstamp_refresh_inline(struct tcp_sock *tp)
+{
+	u64 val = tcp_clock_ns();
+
+	tp->tcp_clock_cache = val;
+	tp->tcp_mstamp = div_u64(val, NSEC_PER_USEC);
+}
 void tcp_mstamp_refresh(struct tcp_sock *tp);
 
 static inline u32 tcp_stamp_us_delta(u64 t1, u64 t0)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index d5c9e65d97606d8eb57aba8ebc2373adf1bed62b..7995a89bafc9d1d997b936eeac3964cdd7e7741a 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6474,7 +6474,7 @@ void tcp_rcv_established(struct sock *sk, struct sk_buff *skb)
 	/* TCP congestion window tracking */
 	trace_tcp_probe(sk, skb);
 
-	tcp_mstamp_refresh(tp);
+	tcp_mstamp_refresh_inline(tp);
 	if (unlikely(!rcu_access_pointer(sk->sk_rx_dst)))
 		inet_csk(sk)->icsk_af_ops->sk_rx_dst_set(sk, skb);
 	/*
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index f9d8755705f762fe4da3064d2b1bfce4828ec0c1..c8d7b5d20d1874bb7840e1c480195076830f1058 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -52,15 +52,9 @@
 
 #include <trace/events/tcp.h>
 
-/* Refresh clocks of a TCP socket,
- * ensuring monotically increasing values.
- */
-void tcp_mstamp_refresh(struct tcp_sock *tp)
+void noinline tcp_mstamp_refresh(struct tcp_sock *tp)
 {
-	u64 val = tcp_clock_ns();
-
-	tp->tcp_clock_cache = val;
-	tp->tcp_mstamp = div_u64(val, NSEC_PER_USEC);
+	tcp_mstamp_refresh_inline(tp);
 }
 
 static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
@@ -2971,7 +2965,7 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
 
 	sent_pkts = 0;
 
-	tcp_mstamp_refresh(tp);
+	tcp_mstamp_refresh_inline(tp);
 
 	/* AccECN option beacon depends on mstamp, it may change mss */
 	if (tcp_ecn_mode_accecn(tp) && tcp_accecn_option_beacon_check(sk))
-- 
2.54.0.545.g6539524ca2-goog

Re: [PATCH net-next] tcp: add tcp_mstamp_refresh_inline()

[Neal Cardwell]

On Tue, Apr 28, 2026 at 9:08 PM Eric Dumazet <edumazet@google.com> wrote:
>
> We want to inline tcp_mstamp_refresh() in fast path only:
>
> - tcp_rcv_established()
> - tcp_write_xmit()
>
> Add tcp_mstamp_refresh_inline() for this purpose.
>
> Add noinline qualifier on tcp_mstamp_refresh() for the other paths,
> to reduce bloat.
>
> $ scripts/bloat-o-meter -t vmlinux.old vmlinux.new
> add/remove: 0/0 grow/shrink: 1/4 up/down: 26/-123 (-97)
> Function                                     old     new   delta
> tcp_rcv_established                         2238    2264     +26
> tcp_connect                                 4027    4003     -24
> tcp_tsq_write                                152     120     -32
> tcp_send_active_reset                        476     444     -32
> tcp_send_window_probe                        235     200     -35
> Total: Before=25316710, After=25316613, chg -0.00%
>
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> ---

Reviewed-by: Neal Cardwell <ncardwell@google.com>

Thanks, Eric!

neal

Re: [PATCH net-next] tcp: add tcp_mstamp_refresh_inline()

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Wed, 29 Apr 2026 01:08:09 +0000 you wrote:
> We want to inline tcp_mstamp_refresh() in fast path only:
> 
> - tcp_rcv_established()
> - tcp_write_xmit()
> 
> Add tcp_mstamp_refresh_inline() for this purpose.
> 
> [...]

Here is the summary with links:
  - [net-next] tcp: add tcp_mstamp_refresh_inline()
    https://git.kernel.org/netdev/net-next/c/28df22acc275

You are awesome, thank you!
-- 
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