[PATCH net-next] tcp: inline tcp_chrono_start()

[PATCH net-next] tcp: inline tcp_chrono_start()

[Eric Dumazet]

tcp_chrono_start() is small enough, and used in TCP sendmsg()
fast path (from tcp_skb_entail()).

Note clang is already inlining it from functions in tcp_output.c.

Inlining it improves performance and reduces bloat :

$ scripts/bloat-o-meter -t vmlinux.old vmlinux.new
add/remove: 0/2 grow/shrink: 1/0 up/down: 1/-84 (-83)
Function                                     old     new   delta
tcp_skb_entail                               280     281      +1
__pfx_tcp_chrono_start                        16       -     -16
tcp_chrono_start                              68       -     -68
Total: Before=25192434, After=25192351, chg -0.00%

Note that tcp_chrono_stop() is too big.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/net/tcp.h     | 25 ++++++++++++++++++++++++-
 net/ipv4/tcp_output.c | 24 ------------------------
 2 files changed, 24 insertions(+), 25 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index a6464142380696e4948a836145ac7aca4ca3ec15..392a1de0d3703b3535431bfd90732186bede3bd7 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -2160,7 +2160,30 @@ enum tcp_chrono {
 	__TCP_CHRONO_MAX,
 };
 
-void tcp_chrono_start(struct sock *sk, const enum tcp_chrono type);
+static inline void tcp_chrono_set(struct tcp_sock *tp, const enum tcp_chrono new)
+{
+	const u32 now = tcp_jiffies32;
+	enum tcp_chrono old = tp->chrono_type;
+
+	if (old > TCP_CHRONO_UNSPEC)
+		tp->chrono_stat[old - 1] += now - tp->chrono_start;
+	tp->chrono_start = now;
+	tp->chrono_type = new;
+}
+
+static inline void tcp_chrono_start(struct sock *sk, const enum tcp_chrono type)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+
+	/* If there are multiple conditions worthy of tracking in a
+	 * chronograph then the highest priority enum takes precedence
+	 * over the other conditions. So that if something "more interesting"
+	 * starts happening, stop the previous chrono and start a new one.
+	 */
+	if (type > tp->chrono_type)
+		tcp_chrono_set(tp, type);
+}
+
 void tcp_chrono_stop(struct sock *sk, const enum tcp_chrono type);
 
 /* This helper is needed, because skb->tcp_tsorted_anchor uses
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index f0ebcc7e287173be6198fd100130e7ba1a1dbf03..00ffb09d2c624ffb82488fd57dc5daca8a31c96f 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2904,30 +2904,6 @@ static bool tcp_small_queue_check(struct sock *sk, const struct sk_buff *skb,
 	return false;
 }
 
-static void tcp_chrono_set(struct tcp_sock *tp, const enum tcp_chrono new)
-{
-	const u32 now = tcp_jiffies32;
-	enum tcp_chrono old = tp->chrono_type;
-
-	if (old > TCP_CHRONO_UNSPEC)
-		tp->chrono_stat[old - 1] += now - tp->chrono_start;
-	tp->chrono_start = now;
-	tp->chrono_type = new;
-}
-
-void tcp_chrono_start(struct sock *sk, const enum tcp_chrono type)
-{
-	struct tcp_sock *tp = tcp_sk(sk);
-
-	/* If there are multiple conditions worthy of tracking in a
-	 * chronograph then the highest priority enum takes precedence
-	 * over the other conditions. So that if something "more interesting"
-	 * starts happening, stop the previous chrono and start a new one.
-	 */
-	if (type > tp->chrono_type)
-		tcp_chrono_set(tp, type);
-}
-
 void tcp_chrono_stop(struct sock *sk, const enum tcp_chrono type)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
-- 
2.53.0.473.g4a7958ca14-goog

Re: [PATCH net-next] tcp: inline tcp_chrono_start()

[Neal Cardwell]

On Sun, Mar 8, 2026 at 8:35 AM Eric Dumazet <edumazet@google.com> wrote:
>
> tcp_chrono_start() is small enough, and used in TCP sendmsg()
> fast path (from tcp_skb_entail()).
>
> Note clang is already inlining it from functions in tcp_output.c.
>
> Inlining it improves performance and reduces bloat :
>
> $ scripts/bloat-o-meter -t vmlinux.old vmlinux.new
> add/remove: 0/2 grow/shrink: 1/0 up/down: 1/-84 (-83)
> Function                                     old     new   delta
> tcp_skb_entail                               280     281      +1
> __pfx_tcp_chrono_start                        16       -     -16
> tcp_chrono_start                              68       -     -68
> Total: Before=25192434, After=25192351, chg -0.00%
>
> Note that tcp_chrono_stop() is too big.
>
> Signed-off-by: Eric Dumazet <edumazet@google.com>

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

Thanks, Eric!

neal

Re: [PATCH net-next] tcp: inline tcp_chrono_start()

[patchwork-bot+netdevbpf]

Hello:

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

On Sun,  8 Mar 2026 12:35:49 +0000 you wrote:
> tcp_chrono_start() is small enough, and used in TCP sendmsg()
> fast path (from tcp_skb_entail()).
> 
> Note clang is already inlining it from functions in tcp_output.c.
> 
> Inlining it improves performance and reduces bloat :
> 
> [...]

Here is the summary with links:
  - [net-next] tcp: inline tcp_chrono_start()
    https://git.kernel.org/netdev/net-next/c/d6d4ff335db2

You are awesome, thank you!
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