Currently packet_pick_tx_queue() is the only caller of
ndo_select_queue() using a fallback argument other than
__netdev_pick_tx.
Leveraging rx queue, we can obtain a similar queue selection
behavior using core helpers. After this change, ndo_select_queue()
is always invoked with __netdev_pick_tx() as fallback.
We can change ndo_select_queue() signature in a followup patch,
dropping an indirect call per transmitted packet in some scenarios
(e.g. TCP syn and XDP generic xmit)
This changes slightly how af packet queue selection happens when
PACKET_QDISC_BYPASS is set. It's now more similar to plan dev_queue_xmit()
tacking in account both XPS and TC mapping.
RFC -> v1:
- initialize sender_cpu to the expected value
Signed-off-by: Paolo Abeni <pab...@redhat.com>
---
Note: the main goal here is getting rid of the fallback() indirect
call in the device drivers implementing ndo_select_queue(). We can
obtain the same result with the INDIRECT_CALL() harness. Both ways
we need to export __netdev_pick_tx() but here we avoid the need
for additional branching.
---
include/linux/netdevice.h | 2 ++
net/core/dev.c | 5 +++--
net/packet/af_packet.c | 15 +++++++--------
3 files changed, 12 insertions(+), 10 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 26f69cf763f4..c75a6216d0f9 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2152,6 +2152,8 @@ static inline void netdev_for_each_tx_queue(struct
net_device *dev,
&qdisc_xmit_lock_key); \
}
+u16 __netdev_pick_tx(struct net_device *dev, struct sk_buff *skb,
+ struct net_device *sb_dev);
struct netdev_queue *netdev_pick_tx(struct net_device *dev,
struct sk_buff *skb,
struct net_device *sb_dev);
diff --git a/net/core/dev.c b/net/core/dev.c
index 2b67f2aa59dd..004d1180671a 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3704,8 +3704,8 @@ u16 dev_pick_tx_cpu_id(struct net_device *dev, struct
sk_buff *skb,
}
EXPORT_SYMBOL(dev_pick_tx_cpu_id);
-static u16 __netdev_pick_tx(struct net_device *dev, struct sk_buff *skb,
- struct net_device *sb_dev)
+u16 __netdev_pick_tx(struct net_device *dev, struct sk_buff *skb,
+ struct net_device *sb_dev)
{
struct sock *sk = skb->sk;
int queue_index = sk_tx_queue_get(sk);
@@ -3729,6 +3729,7 @@ static u16 __netdev_pick_tx(struct net_device *dev,
struct sk_buff *skb,
return queue_index;
}
+EXPORT_SYMBOL(__netdev_pick_tx);
struct netdev_queue *netdev_pick_tx(struct net_device *dev,
struct sk_buff *skb,
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 8376bc1c1508..633d47dba542 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -275,24 +275,23 @@ static bool packet_use_direct_xmit(const struct
packet_sock *po)
return po->xmit == packet_direct_xmit;
}
-static u16 __packet_pick_tx_queue(struct net_device *dev, struct sk_buff *skb,
- struct net_device *sb_dev)
-{
- return dev_pick_tx_cpu_id(dev, skb, sb_dev, NULL);
-}
-
static u16 packet_pick_tx_queue(struct sk_buff *skb)
{
struct net_device *dev = skb->dev;
const struct net_device_ops *ops = dev->netdev_ops;
+ int cpu = raw_smp_processor_id();
u16 queue_index;
+#ifdef CONFIG_XPS
+ skb->sender_cpu = cpu + 1;
+#endif
+ skb_record_rx_queue(skb, cpu % dev->real_num_tx_queues);
if (ops->ndo_select_queue) {
queue_index = ops->ndo_select_queue(dev, skb, NULL,
- __packet_pick_tx_queue);
+ __netdev_pick_tx);
queue_index = netdev_cap_txqueue(dev, queue_index);
} else {
- queue_index = __packet_pick_tx_queue(dev, skb, NULL);
+ queue_index = __netdev_pick_tx(dev, skb, NULL);
}
return queue_index;
--
2.20.1
