netdev - [PATCH net-next] tcp: use __skb_push() in __tcp_transmit

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Message-ID: <20260203044226.3489941-1-edumazet@google.com>
Date: Tue,  3 Feb 2026 04:42:26 +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>, 
	Kuniyuki Iwashima <kuniyu@...gle.com>, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next] tcp: use __skb_push() in __tcp_transmit_skb()

We trust MAX_TCP_HEADER to be large enough.

Using the inlined version of skb_push() trades 8 bytes
of text for better performance of TCP TX fast path.

$ scripts/bloat-o-meter -t vmlinux.old vmlinux.new
add/remove: 0/0 grow/shrink: 1/0 up/down: 8/0 (8)
Function                                     old     new   delta
__tcp_transmit_skb                          3181    3189      +8
Total: Before=24896035, After=24896043, chg +0.00%

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/ipv4/tcp_output.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 597e888af36d..f907f24f74f7 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1565,7 +1565,7 @@ static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb,
 	 */
 	skb->pfmemalloc = 0;
 
-	skb_push(skb, tcp_header_size);
+	__skb_push(skb, tcp_header_size);
 	skb_reset_transport_header(skb);
 
 	skb_orphan(skb);
-- 
2.53.0.rc1.225.gd81095ad13-goog