From mboxrd@z Thu Jan 1 00:00:00 1970 From: Amir Vadai Subject: [PATCH net-next 08/14] net/mlx4_en: mlx4_en_xmit() reads ring->cons once, and ahead of time to avoid stalls Date: Sun, 5 Oct 2014 12:35:16 +0300 Message-ID: <1412501722-25092-9-git-send-email-amirv@mellanox.com> References: <1412501722-25092-1-git-send-email-amirv@mellanox.com> Cc: netdev@vger.kernel.org, Yevgeny Petrilin , Or Gerlitz , Ido Shamay , Amir Vadai To: "David S. Miller" , Eric Dumazet Return-path: Received: from mailp.voltaire.com ([193.47.165.129]:52731 "EHLO mellanox.co.il" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1751637AbaJEJgL (ORCPT ); Sun, 5 Oct 2014 05:36:11 -0400 In-Reply-To: <1412501722-25092-1-git-send-email-amirv@mellanox.com> Sender: netdev-owner@vger.kernel.org List-ID: From: Eric Dumazet Signed-off-by: Eric Dumazet Signed-off-by: Amir Vadai --- drivers/net/ethernet/mellanox/mlx4/en_tx.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) diff --git a/drivers/net/ethernet/mellanox/mlx4/en_tx.c b/drivers/net/ethernet/mellanox/mlx4/en_tx.c index d9aaeb2..99875c8 100644 --- a/drivers/net/ethernet/mellanox/mlx4/en_tx.c +++ b/drivers/net/ethernet/mellanox/mlx4/en_tx.c @@ -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; -- 1.8.3.4