net: remove 'fallback' argument from dev->ndo_select_queue()

After the previous patch, all the callers of ndo_select_queue()
provide as a 'fallback' argument netdev_pick_tx.
The only exceptions are nested calls to ndo_select_queue(),
which pass down the 'fallback' available in the current scope
- still netdev_pick_tx.

We can drop such argument and replace fallback() invocation with
netdev_pick_tx(). This avoids an indirect call per xmit packet
in some scenarios (TCP syn, UDP unconnected, XDP generic, pktgen)
with device drivers implementing such ndo. It also clean the code
a bit.

Tested with ixgbe and CONFIG_FCOE=m

With pktgen using queue xmit:
threads		vanilla 	patched
		(kpps)		(kpps)
1		2334		2428
2		4166		4278
4		7895		8100

 v1 -> v2:
 - rebased after helper's name change

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 6 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 1a76b4fe9b97..357111431ec9 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3689,16 +3689,14 @@ get_cpus_map:
 }
 
 u16 dev_pick_tx_zero(struct net_device *dev, struct sk_buff *skb,
-                     struct net_device *sb_dev,
-                     select_queue_fallback_t fallback)
+                     struct net_device *sb_dev)
 {
         return 0;
 }
 EXPORT_SYMBOL(dev_pick_tx_zero);
 
 u16 dev_pick_tx_cpu_id(struct net_device *dev, struct sk_buff *skb,
-                       struct net_device *sb_dev,
-                       select_queue_fallback_t fallback)
+                       struct net_device *sb_dev)
 {
         return (u16)raw_smp_processor_id() % dev->real_num_tx_queues;
 }
@@ -3748,8 +3746,7 @@ struct netdev_queue *netdev_core_pick_tx(struct net_device *dev,
                 const struct net_device_ops *ops = dev->netdev_ops;
 
                 if (ops->ndo_select_queue)
-                        queue_index = ops->ndo_select_queue(dev, skb, sb_dev,
-                                                            netdev_pick_tx);
+                        queue_index = ops->ndo_select_queue(dev, skb, sb_dev);
                 else
                         queue_index = netdev_pick_tx(dev, skb, sb_dev);