net: dsa: add GRO support via gro_cells

commit e131a5634830047923c694b4ce0c3b31745ff01b upstream.

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>
Cc: Pali Rohár <pali@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/dsa/Kconfig b/net/dsa/Kconfig
index 4183e4ba27a50c3cf52bff9756d0552da612d619..81f620a3c32b1ef627ac6cf65d30640821405ee2 100644 (file)
--- a/net/dsa/Kconfig
+++ b/net/dsa/Kconfig
@@ -8,6 +8,7 @@ config NET_DSA
        tristate "Distributed Switch Architecture"
        depends on HAVE_NET_DSA && MAY_USE_DEVLINK
        depends on BRIDGE || BRIDGE=n
+       select GRO_CELLS
        select NET_SWITCHDEV
        select PHYLINK
        ---help---

diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c
index 601534a5bfe8cb5ec2d962f3dc0336ae1a0da379..598200e9d5226a0a08b0686b607f5db392347368 100644 (file)
--- a/net/dsa/dsa.c
+++ b/net/dsa/dsa.c
@@ -191,7 +191,7 @@ 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 3964c6f7a7c0d7c6436672c221c2d58802f7227c..79d17507609ab3017a86d06a9f3410477f6d6384 100644 (file)
--- a/net/dsa/dsa_priv.h
+++ b/net/dsa/dsa_priv.h
@@ -15,6 +15,7 @@
 #include <linux/netdevice.h>
 #include <linux/netpoll.h>
 #include <net/dsa.h>
+#include <net/gro_cells.h>
 
 enum {
        DSA_NOTIFIER_AGEING_TIME,
@@ -72,6 +73,8 @@ 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 d03c67e761dfa988bffa67a9983f3e6461ddabdd..11f1560de639156c13a49b7d99e5b97093ccd11f 100644 (file)
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -1337,6 +1337,11 @@ 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;
@@ -1347,7 +1352,7 @@ 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);
@@ -1366,6 +1371,8 @@ 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);
@@ -1386,6 +1393,7 @@ 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);
 }