net: dsa: add GRO support via gro_cells

gro_cells lib is used by different encapsulating netdevices, such as
geneve, macsec, vxlan etc. to speed up decapsulated traffic processing.
CPU tag is a sort of "encapsulation", and we can use the same mechs to
greatly improve overall DSA performance.
skbs are passed to the GRO layer after removing CPU tags, so we don't
need any new packet offload types as it was firstly proposed by me in
the first GRO-over-DSA variant [1].

The size of struct gro_cells is sizeof(void *), so hot struct
dsa_slave_priv becomes only 4/8 bytes bigger, and all critical fields
remain in one 32-byte cacheline.
The other positive side effect is that drivers for network devices
that can be shipped as CPU ports of DSA-driven switches can now use
napi_gro_frags() to pass skbs to kernel. Packets built that way are
completely non-linear and are likely being dropped without GRO.

This was tested on to-be-mainlined-soon Ethernet driver that uses
napi_gro_frags(), and the overall performance was on par with the
variant from [1], sometimes even better due to minimal overhead.
net.core.gro_normal_batch tuning may help to push it to the limit
on particular setups and platforms.

iperf3 IPoE VLAN NAT TCP forwarding (port1.218 -> port0) setup
on 1.2 GHz MIPS board:

5.7-rc2 baseline:

[ID]  Interval         Transfer     Bitrate        Retr
[ 5]  0.00-120.01 sec  9.00 GBytes  644 Mbits/sec  413  sender
[ 5]  0.00-120.00 sec  8.99 GBytes  644 Mbits/sec       receiver

Iface      RX packets  TX packets
eth0       7097731     7097702
port0      426050      6671829
port1      6671681     425862
port1.218  6671677     425851

With this patch:

[ID]  Interval         Transfer     Bitrate        Retr
[ 5]  0.00-120.01 sec  12.2 GBytes  870 Mbits/sec  122  sender
[ 5]  0.00-120.00 sec  12.2 GBytes  870 Mbits/sec       receiver

Iface      RX packets  TX packets
eth0       9474792     9474777
port0      455200      353288
port1      9019592     455035
port1.218  353144      455024

v2:
 - Add some performance examples in the commit message;
 - No functional changes.

[1] https://lore.kernel.org/netdev/20191230143028.27313-1-alobakin@dlink.ru/

Signed-off-by: Alexander Lobakin <bloodyreaper@yandex.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/dsa/Kconfig b/net/dsa/Kconfig
index 92663dcb3aa2c235dd9801a1a7a7b68ab42f0b64..739613070d07955b9e9ad24db5a205099ebc97f8 100644 (file)
--- a/net/dsa/Kconfig
+++ b/net/dsa/Kconfig
@@ -9,6 +9,7 @@ menuconfig NET_DSA
        tristate "Distributed Switch Architecture"
        depends on HAVE_NET_DSA
        depends on BRIDGE || BRIDGE=n
+       select GRO_CELLS
        select NET_SWITCHDEV
        select PHYLINK
        select NET_DEVLINK

diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c
index ee2610c4d46a0dd14f538586d7efeea37eca2c5a..0384a911779e28884e0722ee7afb27fd73049fe2 100644 (file)
--- a/net/dsa/dsa.c
+++ b/net/dsa/dsa.c
@@ -234,7 +234,7 @@ static int dsa_switch_rcv(struct sk_buff *skb, struct net_device *dev,
        if (dsa_skb_defer_rx_timestamp(p, skb))
                return 0;
 
-       netif_receive_skb(skb);
+       gro_cells_receive(&p->gcells, skb);
 
        return 0;
 }

diff --git a/net/dsa/dsa_priv.h b/net/dsa/dsa_priv.h
index 904cc7c9b88267647e46c5a81c9b00864c0c2997..6d9a1ef65fa066eb7b0aa223103238ff7473719a 100644 (file)
--- a/net/dsa/dsa_priv.h
+++ b/net/dsa/dsa_priv.h
@@ -11,6 +11,7 @@
 #include <linux/netdevice.h>
 #include <linux/netpoll.h>
 #include <net/dsa.h>
+#include <net/gro_cells.h>
 
 enum {
        DSA_NOTIFIER_AGEING_TIME,
@@ -77,6 +78,8 @@ struct dsa_slave_priv {
 
        struct pcpu_sw_netstats *stats64;
 
+       struct gro_cells        gcells;
+
        /* DSA port data, such as switch, port index, etc. */
        struct dsa_port         *dp;
 

diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index e94eb1aac6029e41b65bd2c1ceb044992aec3a4a..f2c241cf3a8037834ba9f31b4e4c08a6aff1973d 100644 (file)
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -1762,6 +1762,11 @@ int dsa_slave_create(struct dsa_port *port)
                free_netdev(slave_dev);
                return -ENOMEM;
        }
+
+       ret = gro_cells_init(&p->gcells, slave_dev);
+       if (ret)
+               goto out_free;
+
        p->dp = port;
        INIT_LIST_HEAD(&p->mall_tc_list);
        p->xmit = cpu_dp->tag_ops->xmit;
@@ -1781,7 +1786,7 @@ int dsa_slave_create(struct dsa_port *port)
        ret = dsa_slave_phy_setup(slave_dev);
        if (ret) {
                netdev_err(master, "error %d setting up slave phy\n", ret);
-               goto out_free;
+               goto out_gcells;
        }
 
        dsa_slave_notify(slave_dev, DSA_PORT_REGISTER);
@@ -1800,6 +1805,8 @@ out_phy:
        phylink_disconnect_phy(p->dp->pl);
        rtnl_unlock();
        phylink_destroy(p->dp->pl);
+out_gcells:
+       gro_cells_destroy(&p->gcells);
 out_free:
        free_percpu(p->stats64);
        free_netdev(slave_dev);
@@ -1820,6 +1827,7 @@ void dsa_slave_destroy(struct net_device *slave_dev)
        dsa_slave_notify(slave_dev, DSA_PORT_UNREGISTER);
        unregister_netdev(slave_dev);
        phylink_destroy(dp->pl);
+       gro_cells_destroy(&p->gcells);
        free_percpu(p->stats64);
        free_netdev(slave_dev);
 }