From fe971b95c22578456ff7198537827841c726d3f7 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 6 Oct 2014 09:30:35 -0700 Subject: [PATCH] net/mlx4_en: remove NETDEV_TX_BUSY Drivers should avoid NETDEV_TX_BUSY as much as possible. They should stop the tx queue before qdisc even tries to push another packet, to avoid requeues. For a driver supporting skb->xmit_more, this is likely to be a prereq anyway, otherwise we could have a tx deadlock : We need to force a doorbell if TX ring is full. Signed-off-by: Eric Dumazet Acked-by: Amir Vadai Signed-off-by: David S. Miller --- drivers/net/ethernet/mellanox/mlx4/en_tx.c | 48 +++++++++++----------- 1 file changed, 24 insertions(+), 24 deletions(-) diff --git a/drivers/net/ethernet/mellanox/mlx4/en_tx.c b/drivers/net/ethernet/mellanox/mlx4/en_tx.c index 92a7cf46d9af..8726a4aee5a7 100644 --- a/drivers/net/ethernet/mellanox/mlx4/en_tx.c +++ b/drivers/net/ethernet/mellanox/mlx4/en_tx.c @@ -706,6 +706,7 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev) void *fragptr = NULL; bool bounce = false; bool send_doorbell; + bool stop_queue; bool inline_ok; u32 ring_cons; @@ -735,30 +736,6 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev) 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)) > - ring->size - HEADROOM - MAX_DESC_TXBBS)) { - /* every full Tx ring stops queue */ - netif_tx_stop_queue(ring->tx_queue); - ring->queue_stopped++; - - /* If queue was emptied after the if, and before the - * stop_queue - need to wake the queue, or else it will remain - * stopped forever. - * Need a memory barrier to make sure ring->cons was not - * updated before queue was stopped. - */ - wmb(); - - 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++; - } else { - return NETDEV_TX_BUSY; - } - } prefetchw(&ring->tx_queue->dql); @@ -929,6 +906,13 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev) skb_tx_timestamp(skb); + /* Check available TXBBs And 2K spare for prefetch */ + stop_queue = (int)(ring->prod - ring_cons) > + ring->size - HEADROOM - MAX_DESC_TXBBS; + if (unlikely(stop_queue)) { + netif_tx_stop_queue(ring->tx_queue); + ring->queue_stopped++; + } send_doorbell = !skb->xmit_more || netif_xmit_stopped(ring->tx_queue); real_size = (real_size / 16) & 0x3f; @@ -973,6 +957,22 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev) } } + if (unlikely(stop_queue)) { + /* If queue was emptied after the if (stop_queue) , and before + * the netif_tx_stop_queue() - need to wake the queue, + * or else it will remain stopped forever. + * Need a memory barrier to make sure ring->cons was not + * updated before queue was stopped. + */ + smp_rmb(); + + 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++; + } + } return NETDEV_TX_OK; tx_drop_unmap: -- 2.20.1