e1000e: save skb counts in TX to avoid cache misses

In e1000_tx_map, precompute number of segements and bytecounts which
are derived from fields in skb; these are stored in buffer_info.  When
cleaning tx in e1000_clean_tx_irq use the values in the associated
buffer_info for statistics counting, this eliminates cache misses
on skb fields.

Signed-off-by: Tom Herbert <therbert@google.com>
Acked-by: Bruce Allan <bruce.w.allan@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 11 insertions, 9 deletions

diff --git a/drivers/net/e1000e/e1000.h b/drivers/net/e1000e/e1000.h
index 906c4daaabe9..c0b3db40bd73 100644
--- a/drivers/net/e1000e/e1000.h
+++ b/drivers/net/e1000e/e1000.h
@@ -189,6 +189,8 @@ struct e1000_buffer {
                         unsigned long time_stamp;
                         u16 length;
                         u16 next_to_watch;
+                        unsigned int segs;
+                        unsigned int bytecount;
                         u16 mapped_as_page;
                 };
                 /* Rx */
diff --git a/drivers/net/e1000e/netdev.c b/drivers/net/e1000e/netdev.c
index d13760dc27f8..8de64ed8762c 100644
--- a/drivers/net/e1000e/netdev.c
+++ b/drivers/net/e1000e/netdev.c
@@ -1001,14 +1001,8 @@ static bool e1000_clean_tx_irq(struct e1000_adapter *adapter)
                         cleaned = (i == eop);
 
                         if (cleaned) {
-                                struct sk_buff *skb = buffer_info->skb;
-                                unsigned int segs, bytecount;
-                                segs = skb_shinfo(skb)->gso_segs ?: 1;
-                                /* multiply data chunks by size of headers */
-                                bytecount = ((segs - 1) * skb_headlen(skb)) +
-                                            skb->len;
-                                total_tx_packets += segs;
-                                total_tx_bytes += bytecount;
+                                total_tx_packets += buffer_info->segs;
+                                total_tx_bytes += buffer_info->bytecount;
                         }
 
                         e1000_put_txbuf(adapter, buffer_info);
@@ -4261,7 +4255,7 @@ static int e1000_tx_map(struct e1000_adapter *adapter,
         struct e1000_buffer *buffer_info;
         unsigned int len = skb_headlen(skb);
         unsigned int offset = 0, size, count = 0, i;
-        unsigned int f;
+        unsigned int f, bytecount, segs;
 
         i = tx_ring->next_to_use;
 
@@ -4321,7 +4315,13 @@ static int e1000_tx_map(struct e1000_adapter *adapter,
                 }
         }
 
+        segs = skb_shinfo(skb)->gso_segs ?: 1;
+        /* multiply data chunks by size of headers */
+        bytecount = ((segs - 1) * skb_headlen(skb)) + skb->len;
+
         tx_ring->buffer_info[i].skb = skb;
+        tx_ring->buffer_info[i].segs = segs;
+        tx_ring->buffer_info[i].bytecount = bytecount;
         tx_ring->buffer_info[first].next_to_watch = i;
 
         return count;