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@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Signed-off-by: NipaLocal <nipa@local>

Author: edumazet

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)

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;

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