net/mlx4_en: Ignore budget on TX napi polling

It is recommended that TX work not count against the quota.
The cost of TX packet liberation is a minute percentage of what it costs to
process an RX frame. Furthermore, that SKB freeing makes memory available for
other paths in the stack.

Give the TX a larger budget and be more aggressive about cleaning up the Tx
descriptors this budget could be changed using ethtool:
$ ethtool -C eth1 tx-frames-irq <budget>

Signed-off-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 13 insertions, 15 deletions

diff --git a/drivers/net/ethernet/mellanox/mlx4/en_tx.c b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
index ac3dead3792c..5045bab59633 100644
--- a/drivers/net/ethernet/mellanox/mlx4/en_tx.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
@@ -351,9 +351,8 @@ int mlx4_en_free_tx_buf(struct net_device *dev, struct mlx4_en_tx_ring *ring)
         return cnt;
 }
 
-static int mlx4_en_process_tx_cq(struct net_device *dev,
-                                 struct mlx4_en_cq *cq,
-                                 int budget)
+static bool mlx4_en_process_tx_cq(struct net_device *dev,
+                                 struct mlx4_en_cq *cq)
 {
         struct mlx4_en_priv *priv = netdev_priv(dev);
         struct mlx4_cq *mcq = &cq->mcq;
@@ -372,9 +371,10 @@ static int mlx4_en_process_tx_cq(struct net_device *dev,
         int factor = priv->cqe_factor;
         u64 timestamp = 0;
         int done = 0;
+        int budget = priv->tx_work_limit;
 
         if (!priv->port_up)
-                return 0;
+                return true;
 
         index = cons_index & size_mask;
         cqe = &buf[(index << factor) + factor];
@@ -447,7 +447,7 @@ static int mlx4_en_process_tx_cq(struct net_device *dev,
                 netif_tx_wake_queue(ring->tx_queue);
                 ring->wake_queue++;
         }
-        return done;
+        return done < budget;
 }
 
 void mlx4_en_tx_irq(struct mlx4_cq *mcq)
@@ -467,18 +467,16 @@ int mlx4_en_poll_tx_cq(struct napi_struct *napi, int budget)
         struct mlx4_en_cq *cq = container_of(napi, struct mlx4_en_cq, napi);
         struct net_device *dev = cq->dev;
         struct mlx4_en_priv *priv = netdev_priv(dev);
-        int done;
+        int clean_complete;
 
-        done = mlx4_en_process_tx_cq(dev, cq, budget);
+        clean_complete = mlx4_en_process_tx_cq(dev, cq);
+        if (!clean_complete)
+                return budget;
 
-        /* If we used up all the quota - we're probably not done yet... */
-        if (done < budget) {
-                /* Done for now */
-                napi_complete(napi);
-                mlx4_en_arm_cq(priv, cq);
-                return done;
-        }
-        return budget;
+        napi_complete(napi);
+        mlx4_en_arm_cq(priv, cq);
+
+        return 0;
 }
 
 static struct mlx4_en_tx_desc *mlx4_en_bounce_to_desc(struct mlx4_en_priv *priv,