igb: optimize/refactor receive path

While cleaning up the skb_over panic with small frames I found there was
room for improvement in the ordering of operations within the rx receive
flow.  These changes will place the prefetch for the next descriptor to a
point earlier in the rx path.

Signed-off-by: Alexander Duyck <alexander.h.duyck@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, 22 deletions

diff --git a/drivers/net/igb/igb_main.c b/drivers/net/igb/igb_main.c
index 8b80fe343435..21f0c229b64e 100644
--- a/drivers/net/igb/igb_main.c
+++ b/drivers/net/igb/igb_main.c
@@ -3803,6 +3803,7 @@ static bool igb_clean_rx_irq_adv(struct igb_ring *rx_ring,
         unsigned int total_bytes = 0, total_packets = 0;
 
         i = rx_ring->next_to_clean;
+        buffer_info = &rx_ring->buffer_info[i];
         rx_desc = E1000_RX_DESC_ADV(*rx_ring, i);
         staterr = le32_to_cpu(rx_desc->wb.upper.status_error);
 
@@ -3810,25 +3811,22 @@ static bool igb_clean_rx_irq_adv(struct igb_ring *rx_ring,
                 if (*work_done >= budget)
                         break;
                 (*work_done)++;
-                buffer_info = &rx_ring->buffer_info[i];
 
-                /* HW will not DMA in data larger than the given buffer, even
-                 * if it parses the (NFS, of course) header to be larger.  In
-                 * that case, it fills the header buffer and spills the rest
-                 * into the page.
-                 */
-                hlen = (le16_to_cpu(rx_desc->wb.lower.lo_dword.hdr_info) &
-                  E1000_RXDADV_HDRBUFLEN_MASK) >> E1000_RXDADV_HDRBUFLEN_SHIFT;
-                if (hlen > adapter->rx_ps_hdr_size)
-                        hlen = adapter->rx_ps_hdr_size;
+                skb = buffer_info->skb;
+                prefetch(skb->data - NET_IP_ALIGN);
+                buffer_info->skb = NULL;
+
+                i++;
+                if (i == rx_ring->count)
+                        i = 0;
+                next_rxd = E1000_RX_DESC_ADV(*rx_ring, i);
+                prefetch(next_rxd);
+                next_buffer = &rx_ring->buffer_info[i];
 
                 length = le16_to_cpu(rx_desc->wb.upper.length);
                 cleaned = true;
                 cleaned_count++;
 
-                skb = buffer_info->skb;
-                prefetch(skb->data - NET_IP_ALIGN);
-                buffer_info->skb = NULL;
                 if (!adapter->rx_ps_hdr_size) {
                         pci_unmap_single(pdev, buffer_info->dma,
                                          adapter->rx_buffer_len +
@@ -3838,6 +3836,16 @@ static bool igb_clean_rx_irq_adv(struct igb_ring *rx_ring,
                         goto send_up;
                 }
 
+                /* HW will not DMA in data larger than the given buffer, even
+                 * if it parses the (NFS, of course) header to be larger.  In
+                 * that case, it fills the header buffer and spills the rest
+                 * into the page.
+                 */
+                hlen = (le16_to_cpu(rx_desc->wb.lower.lo_dword.hdr_info) &
+                  E1000_RXDADV_HDRBUFLEN_MASK) >> E1000_RXDADV_HDRBUFLEN_SHIFT;
+                if (hlen > adapter->rx_ps_hdr_size)
+                        hlen = adapter->rx_ps_hdr_size;
+
                 if (!skb_shinfo(skb)->nr_frags) {
                         pci_unmap_single(pdev, buffer_info->dma,
                                          adapter->rx_ps_hdr_size +
@@ -3867,13 +3875,6 @@ static bool igb_clean_rx_irq_adv(struct igb_ring *rx_ring,
 
                         skb->truesize += length;
                 }
-send_up:
-                i++;
-                if (i == rx_ring->count)
-                        i = 0;
-                next_rxd = E1000_RX_DESC_ADV(*rx_ring, i);
-                prefetch(next_rxd);
-                next_buffer = &rx_ring->buffer_info[i];
 
                 if (!(staterr & E1000_RXD_STAT_EOP)) {
                         buffer_info->skb = next_buffer->skb;
@@ -3882,7 +3883,7 @@ send_up:
                         next_buffer->dma = 0;
                         goto next_desc;
                 }
-
+send_up:
                 if (staterr & E1000_RXDEXT_ERR_FRAME_ERR_MASK) {
                         dev_kfree_skb_irq(skb);
                         goto next_desc;
@@ -3909,7 +3910,6 @@ next_desc:
                 /* use prefetched values */
                 rx_desc = next_rxd;
                 buffer_info = next_buffer;
-
                 staterr = le32_to_cpu(rx_desc->wb.upper.status_error);
         }