net/mlx4_en: Wake TX queues only when there's enough room

[ Upstream commit 488a9b48e398b157703766e2cd91ea45ac6997c5 ]

Indication of a single completed packet, marked by txbbs_skipped
being bigger then zero, in not enough in order to wake up a
stopped TX queue. The completed packet may contain a single TXBB,
while next packet to be sent (after the wake up) may have multiple
TXBBs (LSO/TSO packets for example), causing overflow in queue followed
by WQE corruption and TX queue timeout.
Instead, wake the stopped queue only when there's enough room for the
worst case (maximum sized WQE) packet that we should need to handle after
the queue is opened again.

Also created an helper routine - mlx4_en_is_tx_ring_full, which checks
if the current TX ring is full or not. It provides better code readability
and removes code duplication.

Signed-off-by: Ido Shamay <idos@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/net/ethernet/mellanox/mlx4/en_tx.c b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
index 998615b536116004ff1d908b6fbdaa330dc873e9..35dd887447d668fde29160307282dcd4e7932cdb 100644 (file)
--- a/drivers/net/ethernet/mellanox/mlx4/en_tx.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
@@ -66,6 +66,7 @@ int mlx4_en_create_tx_ring(struct mlx4_en_priv *priv,
        ring->size = size;
        ring->size_mask = size - 1;
        ring->stride = stride;
+       ring->full_size = ring->size - HEADROOM - MAX_DESC_TXBBS;
 
        tmp = size * sizeof(struct mlx4_en_tx_info);
        ring->tx_info = kmalloc_node(tmp, GFP_KERNEL | __GFP_NOWARN, node);
@@ -232,6 +233,11 @@ void mlx4_en_deactivate_tx_ring(struct mlx4_en_priv *priv,
                       MLX4_QP_STATE_RST, NULL, 0, 0, &ring->qp);
 }
 
+static inline bool mlx4_en_is_tx_ring_full(struct mlx4_en_tx_ring *ring)
+{
+       return ring->prod - ring->cons > ring->full_size;
+}
+
 static void mlx4_en_stamp_wqe(struct mlx4_en_priv *priv,
                              struct mlx4_en_tx_ring *ring, int index,
                              u8 owner)
@@ -474,11 +480,10 @@ static bool mlx4_en_process_tx_cq(struct net_device *dev,
 
        netdev_tx_completed_queue(ring->tx_queue, packets, bytes);
 
-       /*
-        * Wakeup Tx queue if this stopped, and at least 1 packet
-        * was completed
+       /* Wakeup Tx queue if this stopped, and ring is not full.
         */
-       if (netif_tx_queue_stopped(ring->tx_queue) && txbbs_skipped > 0) {
+       if (netif_tx_queue_stopped(ring->tx_queue) &&
+           !mlx4_en_is_tx_ring_full(ring)) {
                netif_tx_wake_queue(ring->tx_queue);
                ring->wake_queue++;
        }
@@ -922,8 +927,7 @@ 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;
+       stop_queue = mlx4_en_is_tx_ring_full(ring);
        if (unlikely(stop_queue)) {
                netif_tx_stop_queue(ring->tx_queue);
                ring->queue_stopped++;
@@ -992,8 +996,7 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev)
                smp_rmb();
 
                ring_cons = ACCESS_ONCE(ring->cons);
-               if (unlikely(((int)(ring->prod - ring_cons)) <=
-                            ring->size - HEADROOM - MAX_DESC_TXBBS)) {
+               if (unlikely(!mlx4_en_is_tx_ring_full(ring))) {
                        netif_tx_wake_queue(ring->tx_queue);
                        ring->wake_queue++;
                }

diff --git a/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h b/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
index c3e4dfd4a29cec8dbb2b857d2bad6b46a7fdf6cb..0bf0fdd5d2b52685aaecd9df1b5f07ae06d37ba4 100644 (file)
--- a/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
+++ b/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
@@ -280,6 +280,7 @@ struct mlx4_en_tx_ring {
        u32                     size; /* number of TXBBs */
        u32                     size_mask;
        u16                     stride;
+       u32                     full_size;
        u16                     cqn;    /* index of port CQ associated with this ring */
        u32                     buf_size;
        __be32                  doorbell_qpn;