igb: reduce cache misses on tx cleanup

This patch reduces the number of skb cache misses in the
clean_tx_irq path, and results in an overall increase
in tx packet throughput.

Signed-off-by: Nicholas Nunley <nicholasx.d.nunley@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 22 insertions, 27 deletions

diff --git a/drivers/net/igb/igb.h b/drivers/net/igb/igb.h
index 735ede9c7d75..6e63d9a7fc75 100644
--- a/drivers/net/igb/igb.h
+++ b/drivers/net/igb/igb.h
@@ -141,8 +141,10 @@ struct igb_buffer {
                         unsigned long time_stamp;
                         u16 length;
                         u16 next_to_watch;
-                        u16 mapped_as_page;
+                        unsigned int bytecount;
                         u16 gso_segs;
+                        union skb_shared_tx shtx;
+                        u8 mapped_as_page;
                 };
                 /* RX */
                 struct {
diff --git a/drivers/net/igb/igb_main.c b/drivers/net/igb/igb_main.c
index 438737d58688..589cf4a6427a 100644
--- a/drivers/net/igb/igb_main.c
+++ b/drivers/net/igb/igb_main.c
@@ -3899,34 +3899,33 @@ static inline int igb_tx_map_adv(struct igb_ring *tx_ring, struct sk_buff *skb,
 {
         struct igb_buffer *buffer_info;
         struct device *dev = tx_ring->dev;
-        unsigned int len = skb_headlen(skb);
+        unsigned int hlen = skb_headlen(skb);
         unsigned int count = 0, i;
         unsigned int f;
+        u16 gso_segs = skb_shinfo(skb)->gso_segs ?: 1;
 
         i = tx_ring->next_to_use;
 
         buffer_info = &tx_ring->buffer_info[i];
-        BUG_ON(len >= IGB_MAX_DATA_PER_TXD);
-        buffer_info->length = len;
+        BUG_ON(hlen >= IGB_MAX_DATA_PER_TXD);
+        buffer_info->length = hlen;
         /* set time_stamp *before* dma to help avoid a possible race */
         buffer_info->time_stamp = jiffies;
         buffer_info->next_to_watch = i;
-        buffer_info->dma = dma_map_single(dev, skb->data, len,
+        buffer_info->dma = dma_map_single(dev, skb->data, hlen,
                                           DMA_TO_DEVICE);
         if (dma_mapping_error(dev, buffer_info->dma))
                 goto dma_error;
 
         for (f = 0; f < skb_shinfo(skb)->nr_frags; f++) {
-                struct skb_frag_struct *frag;
+                struct skb_frag_struct *frag = &skb_shinfo(skb)->frags[f];
+                unsigned int len = frag->size;
 
                 count++;
                 i++;
                 if (i == tx_ring->count)
                         i = 0;
 
-                frag = &skb_shinfo(skb)->frags[f];
-                len = frag->size;
-
                 buffer_info = &tx_ring->buffer_info[i];
                 BUG_ON(len >= IGB_MAX_DATA_PER_TXD);
                 buffer_info->length = len;
@@ -3944,7 +3943,10 @@ static inline int igb_tx_map_adv(struct igb_ring *tx_ring, struct sk_buff *skb,
         }
 
         tx_ring->buffer_info[i].skb = skb;
-        tx_ring->buffer_info[i].gso_segs = skb_shinfo(skb)->gso_segs ?: 1;
+        tx_ring->buffer_info[i].shtx = skb_shinfo(skb)->tx_flags;
+        /* multiply data chunks by size of headers */
+        tx_ring->buffer_info[i].bytecount = ((gso_segs - 1) * hlen) + skb->len;
+        tx_ring->buffer_info[i].gso_segs = gso_segs;
         tx_ring->buffer_info[first].next_to_watch = i;
 
         return ++count;
@@ -5288,22 +5290,21 @@ static void igb_systim_to_hwtstamp(struct igb_adapter *adapter,
 /**
  * igb_tx_hwtstamp - utility function which checks for TX time stamp
  * @q_vector: pointer to q_vector containing needed info
- * @skb: packet that was just sent
+ * @buffer: pointer to igb_buffer structure
  *
  * If we were asked to do hardware stamping and such a time stamp is
  * available, then it must have been for this skb here because we only
  * allow only one such packet into the queue.
  */
-static void igb_tx_hwtstamp(struct igb_q_vector *q_vector, struct sk_buff *skb)
+static void igb_tx_hwtstamp(struct igb_q_vector *q_vector, struct igb_buffer *buffer_info)
 {
         struct igb_adapter *adapter = q_vector->adapter;
-        union skb_shared_tx *shtx = skb_tx(skb);
         struct e1000_hw *hw = &adapter->hw;
         struct skb_shared_hwtstamps shhwtstamps;
         u64 regval;
 
         /* if skb does not support hw timestamp or TX stamp not valid exit */
-        if (likely(!shtx->hardware) ||
+        if (likely(!buffer_info->shtx.hardware) ||
             !(rd32(E1000_TSYNCTXCTL) & E1000_TSYNCTXCTL_VALID))
                 return;
 
@@ -5311,7 +5312,7 @@ static void igb_tx_hwtstamp(struct igb_q_vector *q_vector, struct sk_buff *skb)
         regval |= (u64)rd32(E1000_TXSTMPH) << 32;
 
         igb_systim_to_hwtstamp(adapter, &shhwtstamps, regval);
-        skb_tstamp_tx(skb, &shhwtstamps);
+        skb_tstamp_tx(buffer_info->skb, &shhwtstamps);
 }
 
 /**
@@ -5326,7 +5327,6 @@ static bool igb_clean_tx_irq(struct igb_q_vector *q_vector)
         struct net_device *netdev = tx_ring->netdev;
         struct e1000_hw *hw = &adapter->hw;
         struct igb_buffer *buffer_info;
-        struct sk_buff *skb;
         union e1000_adv_tx_desc *tx_desc, *eop_desc;
         unsigned int total_bytes = 0, total_packets = 0;
         unsigned int i, eop, count = 0;
@@ -5342,19 +5342,12 @@ static bool igb_clean_tx_irq(struct igb_q_vector *q_vector)
                         tx_desc = E1000_TX_DESC_ADV(*tx_ring, i);
                         buffer_info = &tx_ring->buffer_info[i];
                         cleaned = (i == eop);
-                        skb = buffer_info->skb;
 
-                        if (skb) {
-                                unsigned int segs, bytecount;
+                        if (buffer_info->skb) {
+                                total_bytes += buffer_info->bytecount;
                                 /* gso_segs is currently only valid for tcp */
-                                segs = buffer_info->gso_segs;
-                                /* multiply data chunks by size of headers */
-                                bytecount = ((segs - 1) * skb_headlen(skb)) +
-                                            skb->len;
-                                total_packets += segs;
-                                total_bytes += bytecount;
-
-                                igb_tx_hwtstamp(q_vector, skb);
+                                total_packets += buffer_info->gso_segs;
+                                igb_tx_hwtstamp(q_vector, buffer_info);
                         }
 
                         igb_unmap_and_free_tx_resource(tx_ring, buffer_info);