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>

diff --git a/drivers/net/e1000e/e1000.h b/drivers/net/e1000e/e1000.h
index 906c4da..c0b3db4 100644 (file)
--- 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 d13760d..8de64ed 100644 (file)
--- 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;