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Commit cb53fd54 authored by David S. Miller's avatar David S. Miller
Browse files

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: default avatarDavid S. Miller <davem@davemloft.net>
parents b8a5d06a c2973444

drivers/net/ethernet/mellanox/mlx4/en_tx.c

+4 −2
Original line number Diff line number Diff line
@@ -1006,7 +1006,6 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev) 
		ring->packets++;

	}

	ring->bytes += tx_info->nr_bytes;

	netdev_tx_sent_queue(ring->tx_queue, tx_info->nr_bytes);

	AVG_PERF_COUNTER(priv->pstats.tx_pktsz_avg, skb->len);



	if (tx_info->inl)
@@ -1044,7 +1043,10 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev) 
		netif_tx_stop_queue(ring->tx_queue);

		ring->queue_stopped++;

	}

	send_doorbell = !skb->xmit_more || netif_xmit_stopped(ring->tx_queue);



	send_doorbell = __netdev_tx_sent_queue(ring->tx_queue,

					       tx_info->nr_bytes,

					       skb->xmit_more);



	real_size = (real_size / 16) & 0x3f;

include/linux/netdevice.h

+20 −0
Original line number Diff line number Diff line
@@ -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

net/core/dev.c

+1 −1
Original line number Diff line number Diff line
@@ -3272,7 +3272,7 @@ struct sk_buff *dev_hard_start_xmit(struct sk_buff *first, struct net_device *de 
		}



		skb = next;

		if (netif_xmit_stopped(txq) && skb) {

		if (netif_tx_queue_stopped(txq) && skb) {

			rc = NETDEV_TX_BUSY;

			break;

		}