target/linux/generic/backport-5.4/755-v5.8-net-dsa-add-GRO-support-via-gro_cells.patch

   1 From: Alexander Lobakin <bloodyreaper@yandex.ru>
   2 Date: Tue, 21 Apr 2020 16:41:08 +0300
   3 Subject: [PATCH] net: dsa: add GRO support via gro_cells
   4
   5 gro_cells lib is used by different encapsulating netdevices, such as
   6 geneve, macsec, vxlan etc. to speed up decapsulated traffic processing.
   7 CPU tag is a sort of "encapsulation", and we can use the same mechs to
   8 greatly improve overall DSA performance.
   9 skbs are passed to the GRO layer after removing CPU tags, so we don't
  10 need any new packet offload types as it was firstly proposed by me in
  11 the first GRO-over-DSA variant [1].
  12
  13 The size of struct gro_cells is sizeof(void *), so hot struct
  14 dsa_slave_priv becomes only 4/8 bytes bigger, and all critical fields
  15 remain in one 32-byte cacheline.
  16 The other positive side effect is that drivers for network devices
  17 that can be shipped as CPU ports of DSA-driven switches can now use
  18 napi_gro_frags() to pass skbs to kernel. Packets built that way are
  19 completely non-linear and are likely being dropped without GRO.
  20
  21 This was tested on to-be-mainlined-soon Ethernet driver that uses
  22 napi_gro_frags(), and the overall performance was on par with the
  23 variant from [1], sometimes even better due to minimal overhead.
  24 net.core.gro_normal_batch tuning may help to push it to the limit
  25 on particular setups and platforms.
  26
  27 iperf3 IPoE VLAN NAT TCP forwarding (port1.218 -> port0) setup
  28 on 1.2 GHz MIPS board:
  29
  30 5.7-rc2 baseline:
  31
  32 [ID]  Interval         Transfer     Bitrate        Retr
  33 [ 5]  0.00-120.01 sec  9.00 GBytes  644 Mbits/sec  413  sender
  34 [ 5]  0.00-120.00 sec  8.99 GBytes  644 Mbits/sec       receiver
  35
  36 Iface      RX packets  TX packets
  37 eth0       7097731     7097702
  38 port0      426050      6671829
  39 port1      6671681     425862
  40 port1.218  6671677     425851
  41
  42 With this patch:
  43
  44 [ID]  Interval         Transfer     Bitrate        Retr
  45 [ 5]  0.00-120.01 sec  12.2 GBytes  870 Mbits/sec  122  sender
  46 [ 5]  0.00-120.00 sec  12.2 GBytes  870 Mbits/sec       receiver
  47
  48 Iface      RX packets  TX packets
  49 eth0       9474792     9474777
  50 port0      455200      353288
  51 port1      9019592     455035
  52 port1.218  353144      455024
  53
  54 v2:
  55  - Add some performance examples in the commit message;
  56  - No functional changes.
  57
  58 [1] https://lore.kernel.org/netdev/20191230143028.27313-1-alobakin@dlink.ru/
  59
  60 Signed-off-by: Alexander Lobakin <bloodyreaper@yandex.ru>
  61 Signed-off-by: David S. Miller <davem@davemloft.net>
  62 ---
  63
  64 --- a/net/dsa/Kconfig
  65 +++ b/net/dsa/Kconfig
  66 @@ -9,6 +9,7 @@ menuconfig NET_DSA
  67         tristate "Distributed Switch Architecture"
  68         depends on HAVE_NET_DSA
  69         depends on BRIDGE || BRIDGE=n
  70 +       select GRO_CELLS
  71         select NET_SWITCHDEV
  72         select PHYLINK
  73         select NET_DEVLINK
  74 --- a/net/dsa/dsa.c
  75 +++ b/net/dsa/dsa.c
  76 @@ -238,7 +238,7 @@ static int dsa_switch_rcv(struct sk_buff
  77         if (dsa_skb_defer_rx_timestamp(p, skb))
  78                 return 0;
  79
  80 -       netif_receive_skb(skb);
  81 +       gro_cells_receive(&p->gcells, skb);
  82
  83         return 0;
  84  }
  85 --- a/net/dsa/dsa_priv.h
  86 +++ b/net/dsa/dsa_priv.h
  87 @@ -11,6 +11,7 @@
  88  #include <linux/netdevice.h>
  89  #include <linux/netpoll.h>
  90  #include <net/dsa.h>
  91 +#include <net/gro_cells.h>
  92
  93  enum {
  94         DSA_NOTIFIER_AGEING_TIME,
  95 @@ -68,6 +69,8 @@ struct dsa_slave_priv {
  96
  97         struct pcpu_sw_netstats *stats64;
  98
  99 +       struct gro_cells        gcells;
 100 +
 101         /* DSA port data, such as switch, port index, etc. */
 102         struct dsa_port         *dp;
 103
 104 --- a/net/dsa/slave.c
 105 +++ b/net/dsa/slave.c
 106 @@ -1431,6 +1431,11 @@ int dsa_slave_create(struct dsa_port *po
 107                 free_netdev(slave_dev);
 108                 return -ENOMEM;
 109         }
 110 +
 111 +       ret = gro_cells_init(&p->gcells, slave_dev);
 112 +       if (ret)
 113 +               goto out_free;
 114 +
 115         p->dp = port;
 116         INIT_LIST_HEAD(&p->mall_tc_list);
 117         INIT_WORK(&port->xmit_work, dsa_port_xmit_work);
 118 @@ -1443,7 +1448,7 @@ int dsa_slave_create(struct dsa_port *po
 119         ret = dsa_slave_phy_setup(slave_dev);
 120         if (ret) {
 121                 netdev_err(master, "error %d setting up slave phy\n", ret);
 122 -               goto out_free;
 123 +               goto out_gcells;
 124         }
 125
 126         dsa_slave_notify(slave_dev, DSA_PORT_REGISTER);
 127 @@ -1462,6 +1467,8 @@ out_phy:
 128         phylink_disconnect_phy(p->dp->pl);
 129         rtnl_unlock();
 130         phylink_destroy(p->dp->pl);
 131 +out_gcells:
 132 +       gro_cells_destroy(&p->gcells);
 133  out_free:
 134         free_percpu(p->stats64);
 135         free_netdev(slave_dev);
 136 @@ -1482,6 +1489,7 @@ void dsa_slave_destroy(struct net_device
 137         dsa_slave_notify(slave_dev, DSA_PORT_UNREGISTER);
 138         unregister_netdev(slave_dev);
 139         phylink_destroy(dp->pl);
 140 +       gro_cells_destroy(&p->gcells);
 141         free_percpu(p->stats64);
 142         free_netdev(slave_dev);
 143  }