ipv6: Move ipv6_fl_list from ipv6_pinfo to inet_sock.

In {tcp6,udp6,raw6}_sock, struct ipv6_pinfo is always placed at
the beginning of a new cache line because

  1. __alignof__(struct tcp_sock) is 64 due to ____cacheline_aligned
     of __cacheline_group_begin(tcp_sock_write_tx)

  2. __alignof__(struct udp_sock) is 64 due to ____cacheline_aligned
     of struct numa_drop_counters

  3. in raw6_sock, struct numa_drop_counters is placed before
     struct ipv6_pinfo

.  struct ipv6_pinfo is 136 bytes, but the last cache line is
only used by ipv6_fl_list:

  $ pahole -C ipv6_pinfo vmlinux
  struct ipv6_pinfo {
  ...
  	/* --- cacheline 2 boundary (128 bytes) --- */
  	struct ipv6_fl_socklist *  ipv6_fl_list;         /*   128     8 */

  	/* size: 136, cachelines: 3, members: 23 */

Let's move ipv6_fl_list from struct ipv6_pinfo to struct inet_sock
to save a full cache line for {tcp6,udp6,raw6}_sock.

Now, struct ipv6_pinfo is 128 bytes, and {tcp6,udp6,raw6}_sock have
64 bytes less, while {tcp,udp,raw}_sock retain the same size.

Before:

  # grep -E "^(RAW|UDP[^L\-]|TCP)" /proc/slabinfo | awk '{print $1, "\t", $4}'
  RAWv6 	 1408
  UDPv6 	 1472
  TCPv6 	 2560
  RAW 		 1152
  UDP	 	 1280
  TCP 		 2368

After:

  # grep -E "^(RAW|UDP[^L\-]|TCP)" /proc/slabinfo | awk '{print $1, "\t", $4}'
  RAWv6 	 1344
  UDPv6 	 1408
  TCPv6 	 2496
  RAW 		 1152
  UDP	 	 1280
  TCP 		 2368

Also, ipv6_fl_list and inet_flags (SNDFLOW bit) are placed in the
same cache line.

  $ pahole -C inet_sock vmlinux
  ...
  	/* --- cacheline 11 boundary (704 bytes) was 56 bytes ago --- */
  	struct ipv6_pinfo *        pinet6;               /*   760     8 */
  	/* --- cacheline 12 boundary (768 bytes) --- */
  	struct ipv6_fl_socklist *  ipv6_fl_list;         /*   768     8 */
  	unsigned long              inet_flags;           /*   776     8 */

Doc churn is due to the insufficient Type column (only 1 space short).

Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20251014224210.2964778-1-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 40 insertions, 39 deletions

diff --git a/Documentation/networking/net_cachelines/inet_sock.rst b/Documentation/networking/net_cachelines/inet_sock.rst
index b11bf48fa2b3..4c72a28a7012 100644
--- a/Documentation/networking/net_cachelines/inet_sock.rst
+++ b/Documentation/networking/net_cachelines/inet_sock.rst
@@ -5,42 +5,43 @@
 inet_sock struct fast path usage breakdown
 ==========================================
 
-======================= ===================== =================== =================== ======================================================================================================
-Type                    Name                  fastpath_tx_access  fastpath_rx_access  comment
-======================= ===================== =================== =================== ======================================================================================================
-struct sock             sk                    read_mostly         read_mostly         tcp_init_buffer_space,tcp_init_transfer,tcp_finish_connect,tcp_connect,tcp_send_rcvq,tcp_send_syn_data
-struct ipv6_pinfo*      pinet6
-be16                    inet_sport            read_mostly                             __tcp_transmit_skb
-be32                    inet_daddr            read_mostly                             ip_select_ident_segs
-be32                    inet_rcv_saddr
-be16                    inet_dport            read_mostly                             __tcp_transmit_skb
-u16                     inet_num
-be32                    inet_saddr
-s16                     uc_ttl                read_mostly                             __ip_queue_xmit/ip_select_ttl
-u16                     cmsg_flags
-struct ip_options_rcu*  inet_opt              read_mostly                             __ip_queue_xmit
-u16                     inet_id               read_mostly                             ip_select_ident_segs
-u8                      tos                   read_mostly                             ip_queue_xmit
-u8                      min_ttl
-u8                      mc_ttl
-u8                      pmtudisc
-u8:1                    recverr
-u8:1                    is_icsk
-u8:1                    freebind
-u8:1                    hdrincl
-u8:1                    mc_loop
-u8:1                    transparent
-u8:1                    mc_all
-u8:1                    nodefrag
-u8:1                    bind_address_no_port
-u8:1                    recverr_rfc4884
-u8:1                    defer_connect         read_mostly                             tcp_sendmsg_fastopen
-u8                      rcv_tos
-u8                      convert_csum
-int                     uc_index
-int                     mc_index
-be32                    mc_addr
-struct ip_mc_socklist*  mc_list
-struct inet_cork_full   cork                  read_mostly                             __tcp_transmit_skb
-struct                  local_port_range
-======================= ===================== =================== =================== ======================================================================================================
+======================== ===================== =================== =================== ======================================================================================================
+Type                     Name                  fastpath_tx_access  fastpath_rx_access  comment
+======================== ===================== =================== =================== ======================================================================================================
+struct sock              sk                    read_mostly         read_mostly         tcp_init_buffer_space,tcp_init_transfer,tcp_finish_connect,tcp_connect,tcp_send_rcvq,tcp_send_syn_data
+struct ipv6_pinfo*       pinet6
+struct ipv6_fl_socklist* ipv6_fl_list          read_mostly                             tcp_v6_connect,__ip6_datagram_connect,udpv6_sendmsg,rawv6_sendmsg
+be16                     inet_sport            read_mostly                             __tcp_transmit_skb
+be32                     inet_daddr            read_mostly                             ip_select_ident_segs
+be32                     inet_rcv_saddr
+be16                     inet_dport            read_mostly                             __tcp_transmit_skb
+u16                      inet_num
+be32                     inet_saddr
+s16                      uc_ttl                read_mostly                             __ip_queue_xmit/ip_select_ttl
+u16                      cmsg_flags
+struct ip_options_rcu*   inet_opt              read_mostly                             __ip_queue_xmit
+u16                      inet_id               read_mostly                             ip_select_ident_segs
+u8                       tos                   read_mostly                             ip_queue_xmit
+u8                       min_ttl
+u8                       mc_ttl
+u8                       pmtudisc
+u8:1                     recverr
+u8:1                     is_icsk
+u8:1                     freebind
+u8:1                     hdrincl
+u8:1                     mc_loop
+u8:1                     transparent
+u8:1                     mc_all
+u8:1                     nodefrag
+u8:1                     bind_address_no_port
+u8:1                     recverr_rfc4884
+u8:1                     defer_connect         read_mostly                             tcp_sendmsg_fastopen
+u8                       rcv_tos
+u8                       convert_csum
+int                      uc_index
+int                      mc_index
+be32                     mc_addr
+struct ip_mc_socklist*   mc_list
+struct inet_cork_full    cork                  read_mostly                             __tcp_transmit_skb
+struct                   local_port_range
+======================== ===================== =================== =================== ======================================================================================================