netdev - [PATCH net-next 1/2] tcp: tcp_moderate

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Message-ID: <20251117132802.2083206-2-edumazet@google.com>
Date: Mon, 17 Nov 2025 13:28:01 +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 1/2] tcp: tcp_moderate_rcvbuf is only used in rx path

sysctl_tcp_moderate_rcvbuf is only used from tcp_rcvbuf_grow().

Move it to netns_ipv4_read_rx group.

Remove various CACHELINE_ASSERT_GROUP_SIZE() from netns_ipv4_struct_check(),
as they have no real benefit but cause pain for all changes.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 .../networking/net_cachelines/netns_ipv4_sysctl.rst      | 2 +-
 include/net/netns/ipv4.h                                 | 2 +-
 net/core/net_namespace.c                                 | 9 ++-------
 3 files changed, 4 insertions(+), 9 deletions(-)

diff --git a/Documentation/networking/net_cachelines/netns_ipv4_sysctl.rst b/Documentation/networking/net_cachelines/netns_ipv4_sysctl.rst
index 6e7b20afd2d4984233e91d713ee9acd4b2e007f2..5d5d54fb6ab1b2697d06e0b0ba8c0a91b5dbd438 100644
--- a/Documentation/networking/net_cachelines/netns_ipv4_sysctl.rst
+++ b/Documentation/networking/net_cachelines/netns_ipv4_sysctl.rst
@@ -102,7 +102,7 @@ u8                              sysctl_tcp_app_win
 u8                              sysctl_tcp_frto                                                                      tcp_enter_loss
 u8                              sysctl_tcp_nometrics_save                                                            TCP_LAST_ACK/tcp_update_metrics
 u8                              sysctl_tcp_no_ssthresh_metrics_save                                                  TCP_LAST_ACK/tcp_(update/init)_metrics
-u8                              sysctl_tcp_moderate_rcvbuf                   read_mostly         read_mostly         tcp_tso_should_defer(tx);tcp_rcv_space_adjust(rx)
+u8                              sysctl_tcp_moderate_rcvbuf                                       read_mostly         tcp_rcvbuf_grow()
 u8                              sysctl_tcp_tso_win_divisor                   read_mostly                             tcp_tso_should_defer(tcp_write_xmit)
 u8                              sysctl_tcp_workaround_signed_windows                                                 tcp_select_window
 int                             sysctl_tcp_limit_output_bytes                read_mostly                             tcp_small_queue_check(tcp_write_xmit)
diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h
index de9d36acc8e22d3203120d8015b3d172e85de121..11837d3ccc0ab6dbd6eaacc32536c912b3752202 100644
--- a/include/net/netns/ipv4.h
+++ b/include/net/netns/ipv4.h
@@ -74,11 +74,11 @@ struct netns_ipv4 {
 
 	/* TXRX readonly hotpath cache lines */
 	__cacheline_group_begin(netns_ipv4_read_txrx);
-	u8 sysctl_tcp_moderate_rcvbuf;
 	__cacheline_group_end(netns_ipv4_read_txrx);
 
 	/* RX readonly hotpath cache line */
 	__cacheline_group_begin(netns_ipv4_read_rx);
+	u8 sysctl_tcp_moderate_rcvbuf;
 	u8 sysctl_ip_early_demux;
 	u8 sysctl_tcp_early_demux;
 	u8 sysctl_tcp_l3mdev_accept;
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index adcfef55a66f1691cb76d954af32334e532864bb..c8adbbe014518602857b5f36b90da64333fbeafd 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -1223,14 +1223,10 @@ static void __init netns_ipv4_struct_check(void)
 				      sysctl_tcp_wmem);
 	CACHELINE_ASSERT_GROUP_MEMBER(struct netns_ipv4, netns_ipv4_read_tx,
 				      sysctl_ip_fwd_use_pmtu);
-	CACHELINE_ASSERT_GROUP_SIZE(struct netns_ipv4, netns_ipv4_read_tx, 33);
-
-	/* TXRX readonly hotpath cache lines */
-	CACHELINE_ASSERT_GROUP_MEMBER(struct netns_ipv4, netns_ipv4_read_txrx,
-				      sysctl_tcp_moderate_rcvbuf);
-	CACHELINE_ASSERT_GROUP_SIZE(struct netns_ipv4, netns_ipv4_read_txrx, 1);
 
 	/* RX readonly hotpath cache line */
+	CACHELINE_ASSERT_GROUP_MEMBER(struct netns_ipv4, netns_ipv4_read_rx,
+				      sysctl_tcp_moderate_rcvbuf);
 	CACHELINE_ASSERT_GROUP_MEMBER(struct netns_ipv4, netns_ipv4_read_rx,
 				      sysctl_ip_early_demux);
 	CACHELINE_ASSERT_GROUP_MEMBER(struct netns_ipv4, netns_ipv4_read_rx,
@@ -1241,7 +1237,6 @@ static void __init netns_ipv4_struct_check(void)
 				      sysctl_tcp_reordering);
 	CACHELINE_ASSERT_GROUP_MEMBER(struct netns_ipv4, netns_ipv4_read_rx,
 				      sysctl_tcp_rmem);
-	CACHELINE_ASSERT_GROUP_SIZE(struct netns_ipv4, netns_ipv4_read_rx, 22);
 }
 #endif
 
-- 
2.52.0.rc1.455.g30608eb744-goog