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Commit f905c79e authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

net/mlx4_en: mlx4_en_xmit() reads ring->cons once, and ahead of time to avoid stalls 



Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarAmir Vadai <amirv@mellanox.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent fb1843ee

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

+11 −5
Original line number Diff line number Diff line
@@ -691,10 +691,17 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev) 
	void *fragptr;

	bool bounce = false;

	bool send_doorbell;

	u32 ring_cons;



	if (!priv->port_up)

		goto tx_drop;



	tx_ind = skb_get_queue_mapping(skb);

	ring = priv->tx_ring[tx_ind];



	/* fetch ring->cons far ahead before needing it to avoid stall */

	ring_cons = ACCESS_ONCE(ring->cons);



	real_size = get_real_size(skb, dev, &lso_header_size);

	if (unlikely(!real_size))

		goto tx_drop;
@@ -708,13 +715,11 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev) 
		goto tx_drop;

	}



	tx_ind = skb->queue_mapping;

	ring = priv->tx_ring[tx_ind];

	if (vlan_tx_tag_present(skb))

		vlan_tag = vlan_tx_tag_get(skb);



	/* Check available TXBBs And 2K spare for prefetch */

	if (unlikely(((int)(ring->prod - ring->cons)) >

	if (unlikely(((int)(ring->prod - ring_cons)) >

		     ring->size - HEADROOM - MAX_DESC_TXBBS)) {

		/* every full Tx ring stops queue */

		netif_tx_stop_queue(ring->tx_queue);
@@ -728,7 +733,8 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev) 
		 */

		wmb();



		if (unlikely(((int)(ring->prod - ring->cons)) <=

		ring_cons = ACCESS_ONCE(ring->cons);

		if (unlikely(((int)(ring->prod - ring_cons)) <=

			     ring->size - HEADROOM - MAX_DESC_TXBBS)) {

			netif_tx_wake_queue(ring->tx_queue);

			ring->wake_queue++;
@@ -741,7 +747,7 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev) 


	/* Track current inflight packets for performance analysis */

	AVG_PERF_COUNTER(priv->pstats.inflight_avg,

			 (u32) (ring->prod - ring->cons - 1));

			 (u32)(ring->prod - ring_cons - 1));



	/* Packet is good - grab an index and transmit it */

	index = ring->prod & ring->size_mask;