igb: Improve performance and reduce size of igb_tx_map

This change is meant to both improve the performance and reduce the size of
igb_tx_map.  To do this I have expanded the work done in the main loop by
pushing first into tx_buffer.  This allows us to pull in the dma_mapping_error
check, the tx_buffer value assignment, and the initial DMA value assignment to
the Tx descriptor.  The net result is that the function reduces in size by a
little over a 100 bytes and is about 1% or 2% faster.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 22 insertions, 25 deletions

diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index 0a0bd819d95b..7044aaadeca1 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -4188,29 +4188,34 @@ static void igb_tx_map(struct igb_ring *tx_ring,
         struct sk_buff *skb = first->skb;
         struct igb_tx_buffer *tx_buffer;
         union e1000_adv_tx_desc *tx_desc;
+        struct skb_frag_struct *frag;
         dma_addr_t dma;
-        struct skb_frag_struct *frag = &skb_shinfo(skb)->frags[0];
-        unsigned int data_len = skb->data_len;
-        unsigned int size = skb_headlen(skb);
-        unsigned int paylen = skb->len - hdr_len;
+        unsigned int data_len, size;
         u32 tx_flags = first->tx_flags;
         u32 cmd_type = igb_tx_cmd_type(skb, tx_flags);
         u16 i = tx_ring->next_to_use;
 
         tx_desc = IGB_TX_DESC(tx_ring, i);
 
-        igb_tx_olinfo_status(tx_ring, tx_desc, tx_flags, paylen);
+        igb_tx_olinfo_status(tx_ring, tx_desc, tx_flags, skb->len - hdr_len);
+
+        size = skb_headlen(skb);
+        data_len = skb->data_len;
 
         dma = dma_map_single(tx_ring->dev, skb->data, size, DMA_TO_DEVICE);
-        if (dma_mapping_error(tx_ring->dev, dma))
-                goto dma_error;
 
-        /* record length, and DMA address */
-        dma_unmap_len_set(first, len, size);
-        dma_unmap_addr_set(first, dma, dma);
-        tx_desc->read.buffer_addr = cpu_to_le64(dma);
+        tx_buffer = first;
+
+        for (frag = &skb_shinfo(skb)->frags[0];; frag++) {
+                if (dma_mapping_error(tx_ring->dev, dma))
+                        goto dma_error;
+
+                /* record length, and DMA address */
+                dma_unmap_len_set(tx_buffer, len, size);
+                dma_unmap_addr_set(tx_buffer, dma, dma);
+
+                tx_desc->read.buffer_addr = cpu_to_le64(dma);
 
-        for (;;) {
                 while (unlikely(size > IGB_MAX_DATA_PER_TXD)) {
                         tx_desc->read.cmd_type_len =
                                 cpu_to_le32(cmd_type ^ IGB_MAX_DATA_PER_TXD);
@@ -4221,11 +4226,11 @@ static void igb_tx_map(struct igb_ring *tx_ring,
                                 tx_desc = IGB_TX_DESC(tx_ring, 0);
                                 i = 0;
                         }
+                        tx_desc->read.olinfo_status = 0;
 
                         dma += IGB_MAX_DATA_PER_TXD;
                         size -= IGB_MAX_DATA_PER_TXD;
 
-                        tx_desc->read.olinfo_status = 0;
                         tx_desc->read.buffer_addr = cpu_to_le64(dma);
                 }
 
@@ -4240,31 +4245,23 @@ static void igb_tx_map(struct igb_ring *tx_ring,
                         tx_desc = IGB_TX_DESC(tx_ring, 0);
                         i = 0;
                 }
+                tx_desc->read.olinfo_status = 0;
 
                 size = skb_frag_size(frag);
                 data_len -= size;
 
                 dma = skb_frag_dma_map(tx_ring->dev, frag, 0,
-                                   size, DMA_TO_DEVICE);
-                if (dma_mapping_error(tx_ring->dev, dma))
-                        goto dma_error;
+                                       size, DMA_TO_DEVICE);
 
                 tx_buffer = &tx_ring->tx_buffer_info[i];
-                dma_unmap_len_set(tx_buffer, len, size);
-                dma_unmap_addr_set(tx_buffer, dma, dma);
-
-                tx_desc->read.olinfo_status = 0;
-                tx_desc->read.buffer_addr = cpu_to_le64(dma);
-
-                frag++;
         }
 
-        netdev_tx_sent_queue(txring_txq(tx_ring), first->bytecount);
-
         /* write last descriptor with RS and EOP bits */
         cmd_type |= size | IGB_TXD_DCMD;
         tx_desc->read.cmd_type_len = cpu_to_le32(cmd_type);
 
+        netdev_tx_sent_queue(txring_txq(tx_ring), first->bytecount);
+
         /* set the timestamp */
         first->time_stamp = jiffies;