Merge branch 'net-bql-better-deal-with-GSO'

Eric Dumazet says:

====================
net: bql: better deal with GSO

While BQL bulk dequeue works well for TSO packets, it is
not very efficient as soon as GSO is involved.

On a GSO only workload (UDP or TCP), this patch series
can save about 8 % of cpu cycles on a 40Gbit mlx4 NIC,
by keeping optimal batching, and avoiding expensive
doorbells, qdisc requeues and reschedules.

This patch series :

- Add __netdev_tx_sent_queue() so that drivers
  can implement efficient BQL and xmit_more support.

- Implement a work around in dev_hard_start_xmit()
  for drivers not using __netdev_tx_sent_queue()

- changes mlx4 to use __netdev_tx_sent_queue()

v2: Tariq and Willem feedback addressed.
    added __netdev_tx_sent_queue() (Willem suggestion)
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 20 insertions, 0 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index dc1d9ed33b31..857f8abf7b91 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -3190,6 +3190,26 @@ static inline void netdev_tx_sent_queue(struct netdev_queue *dev_queue,
 #endif
 }
 
+/* Variant of netdev_tx_sent_queue() for drivers that are aware
+ * that they should not test BQL status themselves.
+ * We do want to change __QUEUE_STATE_STACK_XOFF only for the last
+ * skb of a batch.
+ * Returns true if the doorbell must be used to kick the NIC.
+ */
+static inline bool __netdev_tx_sent_queue(struct netdev_queue *dev_queue,
+					  unsigned int bytes,
+					  bool xmit_more)
+{
+	if (xmit_more) {
+#ifdef CONFIG_BQL
+		dql_queued(&dev_queue->dql, bytes);
+#endif
+		return netif_tx_queue_stopped(dev_queue);
+	}
+	netdev_tx_sent_queue(dev_queue, bytes);
+	return true;
+}
+
 /**
  * 	netdev_sent_queue - report the number of bytes queued to hardware
  * 	@dev: network device