[PATCH v1 net-next 00/15] udp_tunnel: Speed up UDP tunnel device destruction (Part I)

[Kuniyuki Iwashima <kuniyu@google.com>]

Most of the UDP tunnel devices call synchronize_rcu() twice
during destruction, for example, vxlan has

  1) synchronize_rcu() in udp_tunnel_sock_release()

  2) synchronize_net() in vxlan_sock_release()

The goal of this series is to remove the former, and another
followup series removes the latter.

synchronize_rcu() was added in udp_tunnel_sock_release() by
commit 3cf7203ca620 ("net/tunnel: wait until all sk_user_data
reader finish before releasing the sock").

This was intended to protect the fast path of a dying vxlan
from dereferencing vxlan_sock->sock->sk after sock_orphan()
has set sock->sk to NULL.

Most of the UDP tunnel devices store struct socket to its
private struct, but it is NOT needed in the fast paths;
struct sock is used there, but struct socket is only used
for tunnel setup / teardown.

This is probably because UDP tunnel functions accept struct
socket, but even such functions do not need it, except for
udp_tunnel_sock_release(), which can safely access sk->sk_socket.

The overview of the series:

  Patch 1 -  5 : Convert UDP tunnel helper to take struct sock
  Patch 6      : Small fix for 10-years-old bug
  Patch 7 - 14 : Store struct sock in tunnel devices
  Patch 15     : Remove synchronize_rcu() in udp_tunnel_sock_release()

  (I noted bugs of fou and amt, so Sashiko may point out
   such pre-existing issues in fou, amt, .. and pfcp and tipc,
   but they are orthogonal and I can follow up separately.)

With this change, a script creating/upping vxlan in 4000 netns
runs 10x faster.

  $ cat vxlan.sh
  for i in `seq 1 40`
  do
      (for j in `seq 1 100` ; do
            unshare -n bash -c "ip link add vxlan0 type vxlan id 100 local 127.0.0.1 dstport 4789 && ip link set vxlan0 up";
       done) &
  done
  wait

With bpftrace, we can see vxlan_stop() is significantly faster too.

  bpftrace -e '
  kprobe:vxlan_stop {
          @start[tid] = nsecs;
  }

  kretprobe:vxlan_stop /@start[tid]/ {
          @duration_us = hist((nsecs - @start[tid]) / 1000);
          delete(@start[tid]);
  }

  END {
          printf("\nExecution time of vxlan_stop (us):\n");
  }'

Before:

  # time ./vxlan.sh // without bpftrace
  real  0m50.615s
  user  0m8.171s
  sys   1m45.101s

  @duration_us:
  [4K, 8K)            1266 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@                   |
  [8K, 16K)           1957 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@|
  [16K, 32K)           764 |@@@@@@@@@@@@@@@@@@@@                                |
  [32K, 64K)             6 |                                                    |
  [64K, 128K)            4 |                                                    |
  [128K, 256K)           3 |                                                    |

After:

  # time ./vxlan.sh // without bpftrace
  real  0m5.247s
  user  0m7.956s
  sys   1m47.404s

  @duration_us:
  [16, 32)            3411 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@|
  [32, 64)             383 |@@@@@                                               |
  [64, 128)            107 |@                                                   |
  [128, 256)            79 |@                                                   |
  [256, 512)            16 |                                                    |
  [512, 1K)              2 |                                                    |
  [1K, 2K)               2 |                                                    |


Kuniyuki Iwashima (15):
  udp_tunnel: Pass struct sock to udp_tunnel_sock_release().
  udp_tunnel: Pass struct sock to setup_udp_tunnel_sock().
  udp_tunnel: Pass struct sock to udp_tunnel6_dst_lookup().
  udp_tunnel: Pass struct sock to udp_tunnel_{push,drop}_rx_port().
  udp_tunnel: Pass struct sock to udp_tunnel_notify_{add,del}_rx_port().
  vxlan: Fix potential null-ptr-deref in vxlan_gro_prepare_receive().
  vxlan: Store struct sock in struct vxlan_sock.
  vxlan: Free vxlan_sock with kfree_rcu().
  geneve: Store struct sock in struct geneve_sock.
  bareudp: Store struct sock in struct bareudp_dev.
  fou: Store struct sock in struct fou.
  amt: Store struct sock in struct amt_dev.
  pfcp: Store struct sock in struct pfcp_dev.
  tipc: Store struct sock in struct udp_bearer.
  udp_tunnel: Remove synchronize_rcu() in udp_tunnel_sock_release().

 drivers/infiniband/sw/rxe/rxe_net.c |  6 +--
 drivers/infiniband/sw/rxe/rxe_ns.c  |  4 +-
 drivers/net/amt.c                   | 80 ++++++++++++++---------------
 drivers/net/bareudp.c               | 51 +++++++++---------
 drivers/net/geneve.c                | 54 +++++++++----------
 drivers/net/gtp.c                   | 10 ++--
 drivers/net/ovpn/udp.c              |  2 +-
 drivers/net/pfcp.c                  | 17 +++---
 drivers/net/vxlan/vxlan_core.c      | 60 ++++++++++++----------
 drivers/net/vxlan/vxlan_multicast.c |  8 +--
 drivers/net/wireguard/socket.c      |  8 +--
 include/net/amt.h                   |  2 +-
 include/net/udp_tunnel.h            | 14 ++---
 include/net/vxlan.h                 |  5 +-
 net/ipv4/fou_core.c                 | 21 ++++----
 net/ipv4/udp_tunnel_core.c          | 23 ++++-----
 net/ipv6/ip6_udp_tunnel.c           |  6 +--
 net/l2tp/l2tp_core.c                |  2 +-
 net/rxrpc/local_object.c            |  2 +-
 net/sctp/protocol.c                 | 10 ++--
 net/tipc/udp_media.c                | 32 +++++++-----
 21 files changed, 209 insertions(+), 208 deletions(-)

-- 
2.54.0.545.g6539524ca2-goog