[PATCH net-next] tcp: move sysctl_tcp_shrink_window to netns_ipv4_read_txrx group

[PATCH net-next] tcp: move sysctl_tcp_shrink_window to netns_ipv4_read_txrx group

[Eric Dumazet]

Commit 18fd64d25422 ("netns-ipv4: reorganize netns_ipv4 fast path
variables") missed that __tcp_select_window() is reading
net->ipv4.sysctl_tcp_shrink_window.

Move this field to netns_ipv4_read_txrx group, as __tcp_select_window()
is used both in tx and rx paths.

Saves a potential cache line miss.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/net/netns/ipv4.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h
index 4c249aeaf7f12f8237232a6f3d3f3ed56d0a53d4..38624beff9b34161327d7549fcd0f041c9c91679 100644
--- a/include/net/netns/ipv4.h
+++ b/include/net/netns/ipv4.h
@@ -74,6 +74,7 @@ struct netns_ipv4 {
 
 	/* TXRX readonly hotpath cache lines */
 	__cacheline_group_begin(netns_ipv4_read_txrx);
+	u8		sysctl_tcp_shrink_window;
 	__cacheline_group_end(netns_ipv4_read_txrx);
 
 	/* RX readonly hotpath cache line */
@@ -122,7 +123,6 @@ struct netns_ipv4 {
 #endif
 	bool			fib_has_custom_local_routes;
 	bool			fib_offload_disabled;
-	u8			sysctl_tcp_shrink_window;
 #ifdef CONFIG_IP_ROUTE_CLASSID
 	atomic_t		fib_num_tclassid_users;
 #endif
-- 
2.53.0.473.g4a7958ca14-goog

Re: [PATCH net-next] tcp: move sysctl_tcp_shrink_window to netns_ipv4_read_txrx group

[Kuniyuki Iwashima]

On Sat, Mar 7, 2026 at 1:22 AM Eric Dumazet <edumazet@google.com> wrote:
>
> Commit 18fd64d25422 ("netns-ipv4: reorganize netns_ipv4 fast path
> variables") missed that __tcp_select_window() is reading
> net->ipv4.sysctl_tcp_shrink_window.
>
> Move this field to netns_ipv4_read_txrx group, as __tcp_select_window()
> is used both in tx and rx paths.
>
> Saves a potential cache line miss.
>
> Signed-off-by: Eric Dumazet <edumazet@google.com>

Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>

Re: [PATCH net-next] tcp: move sysctl_tcp_shrink_window to netns_ipv4_read_txrx group

[patchwork-bot+netdevbpf]

Hello:

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

On Sat,  7 Mar 2026 09:22:14 +0000 you wrote:
> Commit 18fd64d25422 ("netns-ipv4: reorganize netns_ipv4 fast path
> variables") missed that __tcp_select_window() is reading
> net->ipv4.sysctl_tcp_shrink_window.
> 
> Move this field to netns_ipv4_read_txrx group, as __tcp_select_window()
> is used both in tx and rx paths.
> 
> [...]

Here is the summary with links:
  - [net-next] tcp: move sysctl_tcp_shrink_window to netns_ipv4_read_txrx group
    https://git.kernel.org/netdev/net-next/c/e8eb33d650cd

You are awesome, thank you!
-- 
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