net/mlx4_en: Saving mem access on data path

Localized the pdev->dev, and using dma_map instead of pci_map
There are multiple map/unmap operations on data path,
optimizing those by saving redundant pointer access.
Those places were identified as hot-spots when running kernel profiling
during some benchmarks.
The fixes had most impact when testing packet rate with small packets,
reducing several % from CPU load, and in some case being the difference
between reaching wire speed or being CPU bound.

Signed-off-by: Yevgeny Petrilin <yevgenyp@mellanox.co.il>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

@@ -1062,6 +1062,7 @@ int mlx4_en_init_netdev(struct mlx4_en_dev *mdev, int port,
 	memset(priv, 0, sizeof(struct mlx4_en_priv));
 	priv->dev = dev;
 	priv->mdev = mdev;
+	priv->ddev = &mdev->pdev->dev;
 	priv->prof = prof;
 	priv->port = port;
 	priv->port_up = false;

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

@@ -48,7 +48,6 @@ static int mlx4_en_alloc_frag(struct mlx4_en_priv *priv,
 			      struct mlx4_en_rx_alloc *ring_alloc,
 			      int i)
 {
-	struct mlx4_en_dev *mdev = priv->mdev;
 	struct mlx4_en_frag_info *frag_info = &priv->frag_info[i];
 	struct mlx4_en_rx_alloc *page_alloc = &ring_alloc[i];
 	struct page *page;
@@ -72,7 +71,7 @@ static int mlx4_en_alloc_frag(struct mlx4_en_priv *priv,
 		skb_frags[i].offset = page_alloc->offset;
 		page_alloc->offset += frag_info->frag_stride;
 	}
-	dma = pci_map_single(mdev->pdev, page_address(skb_frags[i].page) +
+	dma = dma_map_single(priv->ddev, page_address(skb_frags[i].page) +
 			     skb_frags[i].offset, frag_info->frag_size,
 			     PCI_DMA_FROMDEVICE);
 	rx_desc->data[i].addr = cpu_to_be64(dma);
@@ -186,7 +185,6 @@ static void mlx4_en_free_rx_desc(struct mlx4_en_priv *priv,
 				 struct mlx4_en_rx_ring *ring,
 				 int index)
 {
-	struct mlx4_en_dev *mdev = priv->mdev;
 	struct page_frag *skb_frags;
 	struct mlx4_en_rx_desc *rx_desc = ring->buf + (index << ring->log_stride);
 	dma_addr_t dma;
@@ -198,7 +196,7 @@ static void mlx4_en_free_rx_desc(struct mlx4_en_priv *priv,
 		dma = be64_to_cpu(rx_desc->data[nr].addr);
 
 		en_dbg(DRV, priv, "Unmapping buffer at dma:0x%llx\n", (u64) dma);
-		pci_unmap_single(mdev->pdev, dma, skb_frags[nr].size,
+		dma_unmap_single(priv->ddev, dma, skb_frags[nr].size,
 				 PCI_DMA_FROMDEVICE);
 		put_page(skb_frags[nr].page);
 	}
@@ -412,7 +410,6 @@ static int mlx4_en_complete_rx_desc(struct mlx4_en_priv *priv,
 				    int length)
 {
 	struct skb_frag_struct *skb_frags_rx = skb_shinfo(skb)->frags;
-	struct mlx4_en_dev *mdev = priv->mdev;
 	struct mlx4_en_frag_info *frag_info;
 	int nr;
 	dma_addr_t dma;
@@ -435,7 +432,7 @@ static int mlx4_en_complete_rx_desc(struct mlx4_en_priv *priv,
 			goto fail;
 
 		/* Unmap buffer */
-		pci_unmap_single(mdev->pdev, dma, skb_frag_size(&skb_frags_rx[nr]),
+		dma_unmap_single(priv->ddev, dma, skb_frag_size(&skb_frags_rx[nr]),
 				 PCI_DMA_FROMDEVICE);
 	}
 	/* Adjust size of last fragment to match actual length */
@@ -461,7 +458,6 @@ static struct sk_buff *mlx4_en_rx_skb(struct mlx4_en_priv *priv,
 				      struct mlx4_en_rx_alloc *page_alloc,
 				      unsigned int length)
 {
-	struct mlx4_en_dev *mdev = priv->mdev;
 	struct sk_buff *skb;
 	void *va;
 	int used_frags;
@@ -483,10 +479,10 @@ static struct sk_buff *mlx4_en_rx_skb(struct mlx4_en_priv *priv,
 		/* We are copying all relevant data to the skb - temporarily
 		 * synch buffers for the copy */
 		dma = be64_to_cpu(rx_desc->data[0].addr);
-		dma_sync_single_for_cpu(&mdev->pdev->dev, dma, length,
+		dma_sync_single_for_cpu(priv->ddev, dma, length,
 					DMA_FROM_DEVICE);
 		skb_copy_to_linear_data(skb, va, length);
-		dma_sync_single_for_device(&mdev->pdev->dev, dma, length,
+		dma_sync_single_for_device(priv->ddev, dma, length,
 					   DMA_FROM_DEVICE);
 		skb->tail += length;
 	} else {

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

@@ -198,7 +198,6 @@ static u32 mlx4_en_free_tx_desc(struct mlx4_en_priv *priv,
 				struct mlx4_en_tx_ring *ring,
 				int index, u8 owner)
 {
-	struct mlx4_en_dev *mdev = priv->mdev;
 	struct mlx4_en_tx_info *tx_info = &ring->tx_info[index];
 	struct mlx4_en_tx_desc *tx_desc = ring->buf + index * TXBB_SIZE;
 	struct mlx4_wqe_data_seg *data = (void *) tx_desc + tx_info->data_offset;
@@ -214,7 +213,7 @@ static u32 mlx4_en_free_tx_desc(struct mlx4_en_priv *priv,
 	if (likely((void *) tx_desc + tx_info->nr_txbb * TXBB_SIZE <= end)) {
 		if (!tx_info->inl) {
 			if (tx_info->linear) {
-				pci_unmap_single(mdev->pdev,
+				dma_unmap_single(priv->ddev,
 					(dma_addr_t) be64_to_cpu(data->addr),
 					 be32_to_cpu(data->byte_count),
 					 PCI_DMA_TODEVICE);
@@ -223,7 +222,7 @@ static u32 mlx4_en_free_tx_desc(struct mlx4_en_priv *priv,
 
 			for (i = 0; i < frags; i++) {
 				frag = &skb_shinfo(skb)->frags[i];
-				pci_unmap_page(mdev->pdev,
+				dma_unmap_page(priv->ddev,
 					(dma_addr_t) be64_to_cpu(data[i].addr),
 					skb_frag_size(frag), PCI_DMA_TODEVICE);
 			}
@@ -241,7 +240,7 @@ static u32 mlx4_en_free_tx_desc(struct mlx4_en_priv *priv,
 			}
 
 			if (tx_info->linear) {
-				pci_unmap_single(mdev->pdev,
+				dma_unmap_single(priv->ddev,
 					(dma_addr_t) be64_to_cpu(data->addr),
 					 be32_to_cpu(data->byte_count),
 					 PCI_DMA_TODEVICE);
@@ -253,7 +252,7 @@ static u32 mlx4_en_free_tx_desc(struct mlx4_en_priv *priv,
 				if ((void *) data >= end)
 					data = ring->buf;
 				frag = &skb_shinfo(skb)->frags[i];
-				pci_unmap_page(mdev->pdev,
+				dma_unmap_page(priv->ddev,
 					(dma_addr_t) be64_to_cpu(data->addr),
 					 skb_frag_size(frag), PCI_DMA_TODEVICE);
 				++data;
@@ -733,7 +732,7 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev)
 		/* Map fragments */
 		for (i = skb_shinfo(skb)->nr_frags - 1; i >= 0; i--) {
 			frag = &skb_shinfo(skb)->frags[i];
-			dma = skb_frag_dma_map(&mdev->dev->pdev->dev, frag,
+			dma = skb_frag_dma_map(priv->ddev, frag,
 					       0, skb_frag_size(frag),
 					       DMA_TO_DEVICE);
 			data->addr = cpu_to_be64(dma);
@@ -745,7 +744,7 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev)
 
 		/* Map linear part */
 		if (tx_info->linear) {
-			dma = pci_map_single(mdev->dev->pdev, skb->data + lso_header_size,
+			dma = dma_map_single(priv->ddev, skb->data + lso_header_size,
 					     skb_headlen(skb) - lso_header_size, PCI_DMA_TODEVICE);
 			data->addr = cpu_to_be64(dma);
 			data->lkey = cpu_to_be32(mdev->mr.key);

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

@@ -482,6 +482,7 @@ struct mlx4_en_priv {
 	struct mlx4_en_stat_out_mbox hw_stats;
 	int vids[128];
 	bool wol;
+	struct device *ddev;
 };
 
 enum mlx4_en_wol {