mlx4_en: Moving to Interrupts for TX completions

Moving to interrupts instead of polling fpr TX completions
Avoiding situations where skb can be held in by the driver for
a long time (till timer expires).
The change is also necessary for supporting BQL.

Removing comp_lock that was required because we could handle TX
completions from several contexts: Interrupts, timer, polling.
Now there is only interrupts

Signed-off-by: Yevgeny Petrilin <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

Author: Yevgeny Petrilin

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

@@ -124,11 +124,7 @@ int mlx4_en_activate_cq(struct mlx4_en_priv *priv, struct mlx4_en_cq *cq,
 	cq->mcq.comp  = cq->is_tx ? mlx4_en_tx_irq : mlx4_en_rx_irq;
 	cq->mcq.event = mlx4_en_cq_event;
 
-	if (cq->is_tx) {
-		init_timer(&cq->timer);
-		cq->timer.function = mlx4_en_poll_tx_cq;
-		cq->timer.data = (unsigned long) cq;
-	} else {
+	if (!cq->is_tx) {
 		netif_napi_add(cq->dev, &cq->napi, mlx4_en_poll_rx_cq, 64);
 		napi_enable(&cq->napi);
 	}
@@ -151,16 +147,12 @@ void mlx4_en_destroy_cq(struct mlx4_en_priv *priv, struct mlx4_en_cq *cq)
 
 void mlx4_en_deactivate_cq(struct mlx4_en_priv *priv, struct mlx4_en_cq *cq)
 {
-	struct mlx4_en_dev *mdev = priv->mdev;
-
-	if (cq->is_tx)
-		del_timer(&cq->timer);
-	else {
+	if (!cq->is_tx) {
 		napi_disable(&cq->napi);
 		netif_napi_del(&cq->napi);
 	}
 
-	mlx4_cq_free(mdev->dev, &cq->mcq);
+	mlx4_cq_free(priv->mdev->dev, &cq->mcq);
 }
 
 /* Set rx cq moderation parameters */

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

@@ -667,6 +667,10 @@ int mlx4_en_start_port(struct net_device *dev)
 			mlx4_en_deactivate_cq(priv, cq);
 			goto tx_err;
 		}
+
+		/* Arm CQ for TX completions */
+		mlx4_en_arm_cq(priv, cq);
+
 		/* Set initial ownership of all Tx TXBBs to SW (1) */
 		for (j = 0; j < tx_ring->buf_size; j += STAMP_STRIDE)
 			*((u32 *) (tx_ring->buf + j)) = 0xffffffff;

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

@@ -67,8 +67,6 @@ int mlx4_en_create_tx_ring(struct mlx4_en_priv *priv,
 
 	inline_thold = min(inline_thold, MAX_INLINE);
 
-	spin_lock_init(&ring->comp_lock);
-
 	tmp = size * sizeof(struct mlx4_en_tx_info);
 	ring->tx_info = vmalloc(tmp);
 	if (!ring->tx_info)
@@ -377,41 +375,12 @@ void mlx4_en_tx_irq(struct mlx4_cq *mcq)
 {
 	struct mlx4_en_cq *cq = container_of(mcq, struct mlx4_en_cq, mcq);
 	struct mlx4_en_priv *priv = netdev_priv(cq->dev);
-	struct mlx4_en_tx_ring *ring = &priv->tx_ring[cq->ring];
 
-	if (!spin_trylock(&ring->comp_lock))
-		return;
 	mlx4_en_process_tx_cq(cq->dev, cq);
-	mod_timer(&cq->timer, jiffies + 1);
-	spin_unlock(&ring->comp_lock);
+	mlx4_en_arm_cq(priv, cq);
 }
 
 
-void mlx4_en_poll_tx_cq(unsigned long data)
-{
-	struct mlx4_en_cq *cq = (struct mlx4_en_cq *) data;
-	struct mlx4_en_priv *priv = netdev_priv(cq->dev);
-	struct mlx4_en_tx_ring *ring = &priv->tx_ring[cq->ring];
-	u32 inflight;
-
-	INC_PERF_COUNTER(priv->pstats.tx_poll);
-
-	if (!spin_trylock_irq(&ring->comp_lock)) {
-		mod_timer(&cq->timer, jiffies + MLX4_EN_TX_POLL_TIMEOUT);
-		return;
-	}
-	mlx4_en_process_tx_cq(cq->dev, cq);
-	inflight = (u32) (ring->prod - ring->cons - ring->last_nr_txbb);
-
-	/* If there are still packets in flight and the timer has not already
-	 * been scheduled by the Tx routine then schedule it here to guarantee
-	 * completion processing of these packets */
-	if (inflight && priv->port_up)
-		mod_timer(&cq->timer, jiffies + MLX4_EN_TX_POLL_TIMEOUT);
-
-	spin_unlock_irq(&ring->comp_lock);
-}
-
 static struct mlx4_en_tx_desc *mlx4_en_bounce_to_desc(struct mlx4_en_priv *priv,
 						      struct mlx4_en_tx_ring *ring,
 						      u32 index,
@@ -440,25 +409,6 @@ static struct mlx4_en_tx_desc *mlx4_en_bounce_to_desc(struct mlx4_en_priv *priv,
 	return ring->buf + index * TXBB_SIZE;
 }
 
-static inline void mlx4_en_xmit_poll(struct mlx4_en_priv *priv, int tx_ind)
-{
-	struct mlx4_en_cq *cq = &priv->tx_cq[tx_ind];
-	struct mlx4_en_tx_ring *ring = &priv->tx_ring[tx_ind];
-	unsigned long flags;
-
-	/* If we don't have a pending timer, set one up to catch our recent
-	   post in case the interface becomes idle */
-	if (!timer_pending(&cq->timer))
-		mod_timer(&cq->timer, jiffies + MLX4_EN_TX_POLL_TIMEOUT);
-
-	/* Poll the CQ every mlx4_en_TX_MODER_POLL packets */
-	if ((++ring->poll_cnt & (MLX4_EN_TX_POLL_MODER - 1)) == 0)
-		if (spin_trylock_irqsave(&ring->comp_lock, flags)) {
-			mlx4_en_process_tx_cq(priv->dev, cq);
-			spin_unlock_irqrestore(&ring->comp_lock, flags);
-		}
-}
-
 static int is_inline(struct sk_buff *skb, void **pfrag)
 {
 	void *ptr;
@@ -590,7 +540,6 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev)
 	struct mlx4_en_priv *priv = netdev_priv(dev);
 	struct mlx4_en_dev *mdev = priv->mdev;
 	struct mlx4_en_tx_ring *ring;
-	struct mlx4_en_cq *cq;
 	struct mlx4_en_tx_desc *tx_desc;
 	struct mlx4_wqe_data_seg *data;
 	struct skb_frag_struct *frag;
@@ -638,9 +587,6 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev)
 		ring->blocked = 1;
 		priv->port_stats.queue_stopped++;
 
-		/* Use interrupts to find out when queue opened */
-		cq = &priv->tx_cq[tx_ind];
-		mlx4_en_arm_cq(priv, cq);
 		return NETDEV_TX_BUSY;
 	}
 
@@ -788,9 +734,6 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev)
 		iowrite32be(ring->doorbell_qpn, ring->bf.uar->map + MLX4_SEND_DOORBELL);
 	}
 
-	/* Poll CQ here */
-	mlx4_en_xmit_poll(priv, tx_ind);
-
 	return NETDEV_TX_OK;
 
 tx_drop:

drivers/net/ethernet/mellanox/mlx4/mlx4_en.h

@@ -122,7 +122,7 @@ enum {
 #define MLX4_EN_RX_COAL_TARGET	44
 #define MLX4_EN_RX_COAL_TIME	0x10
 
-#define MLX4_EN_TX_COAL_PKTS	5
+#define MLX4_EN_TX_COAL_PKTS	16
 #define MLX4_EN_TX_COAL_TIME	0x80
 
 #define MLX4_EN_RX_RATE_LOW		400000
@@ -255,7 +255,6 @@ struct mlx4_en_tx_ring {
 	unsigned long bytes;
 	unsigned long packets;
 	unsigned long tx_csum;
-	spinlock_t comp_lock;
 	struct mlx4_bf bf;
 	bool bf_enabled;
 };
@@ -308,8 +307,6 @@ struct mlx4_en_cq {
 	spinlock_t              lock;
 	struct net_device      *dev;
 	struct napi_struct	napi;
-	/* Per-core Tx cq processing support */
-	struct timer_list timer;
 	int size;
 	int buf_size;
 	unsigned vector;
@@ -530,7 +527,6 @@ void mlx4_en_deactivate_cq(struct mlx4_en_priv *priv, struct mlx4_en_cq *cq);
 int mlx4_en_set_cq_moder(struct mlx4_en_priv *priv, struct mlx4_en_cq *cq);
 int mlx4_en_arm_cq(struct mlx4_en_priv *priv, struct mlx4_en_cq *cq);
 
-void mlx4_en_poll_tx_cq(unsigned long data);
 void mlx4_en_tx_irq(struct mlx4_cq *mcq);
 u16 mlx4_en_select_queue(struct net_device *dev, struct sk_buff *skb);
 netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev);