i40e/i40evf: carefully fill tx ring

We need to make sure that we stay away from the cache line
where the DD bit (done) may be getting written back for
the transmit ring since the hardware may be writing the
whole cache line for a partial update.

Change-ID: Id0b6dfc01f654def6a2a021af185803be1915d7e
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Catherine Sullivan <catherine.sullivan@intel.com>
Tested-by: Kavindya Deegala <kavindya.s.deegala@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.c b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
index e4497f8e117d743edafee9c4953b43854e7ed741..2081bdb214e58ec2b72d0e679f379ed6efbdd06e 100644 (file)
--- a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
@@ -2102,7 +2102,7 @@ static int i40e_xmit_descriptor_count(struct sk_buff *skb,
 
        /* need: 1 descriptor per page * PAGE_SIZE/I40E_MAX_DATA_PER_TXD,
         *       + 1 desc for skb_head_len/I40E_MAX_DATA_PER_TXD,
-        *       + 2 desc gap to keep tail from touching head,
+        *       + 4 desc gap to avoid the cache line where head is,
         *       + 1 desc for context descriptor,
         * otherwise try next time
         */
@@ -2113,7 +2113,7 @@ static int i40e_xmit_descriptor_count(struct sk_buff *skb,
        count += skb_shinfo(skb)->nr_frags;
 #endif
        count += TXD_USE_COUNT(skb_headlen(skb));
-       if (i40e_maybe_stop_tx(tx_ring, count + 3)) {
+       if (i40e_maybe_stop_tx(tx_ring, count + 4 + 1)) {
                tx_ring->tx_stats.tx_busy++;
                return 0;
        }

diff --git a/drivers/net/ethernet/intel/i40evf/i40e_txrx.c b/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
index 01bfab729b0134b5193515a2de24f7edb8a3010a..b1d87c6a5c35c1a55b07701c549f692d3b4126f2 100644 (file)
--- a/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
+++ b/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
@@ -1482,7 +1482,7 @@ static int i40e_xmit_descriptor_count(struct sk_buff *skb,
 
        /* need: 1 descriptor per page * PAGE_SIZE/I40E_MAX_DATA_PER_TXD,
         *       + 1 desc for skb_head_len/I40E_MAX_DATA_PER_TXD,
-        *       + 2 desc gap to keep tail from touching head,
+        *       + 4 desc gap to avoid the cache line where head is,
         *       + 1 desc for context descriptor,
         * otherwise try next time
         */
@@ -1493,7 +1493,7 @@ static int i40e_xmit_descriptor_count(struct sk_buff *skb,
        count += skb_shinfo(skb)->nr_frags;
 #endif
        count += TXD_USE_COUNT(skb_headlen(skb));
-       if (i40e_maybe_stop_tx(tx_ring, count + 3)) {
+       if (i40e_maybe_stop_tx(tx_ring, count + 4 + 1)) {
                tx_ring->tx_stats.tx_busy++;
                return 0;
        }