e1000: Added a performance enhancement - prefetch

- this implementation of prefetch was tested on new and old hardware

Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: John Ronciak <john.ronciak@intel.com>

1 files changed, 15 insertions, 3 deletions

diff --git a/drivers/net/e1000/e1000_main.c b/drivers/net/e1000/e1000_main.c
index d641fbc7a6e1..b572a1218c81 100644
--- a/drivers/net/e1000/e1000_main.c
+++ b/drivers/net/e1000/e1000_main.c
@@ -3569,10 +3569,15 @@ e1000_clean_rx_irq(struct e1000_adapter *adapter,
                 skb = buffer_info->skb;
                 buffer_info->skb = NULL;
 
+                prefetch(skb->data - NET_IP_ALIGN);
+
                 if (++i == rx_ring->count) i = 0;
                 next_rxd = E1000_RX_DESC(*rx_ring, i);
+                prefetch(next_rxd);
+
                 next_buffer = &rx_ring->buffer_info[i];
                 next_skb = next_buffer->skb;
+                prefetch(next_skb->data - NET_IP_ALIGN);
 
                 cleaned = TRUE;
                 cleaned_count++;
@@ -3668,6 +3673,7 @@ next_desc:
                         cleaned_count = 0;
                 }
 
+                /* use prefetched values */
                 rx_desc = next_rxd;
                 buffer_info = next_buffer;
         }
@@ -3710,9 +3716,9 @@ e1000_clean_rx_irq_ps(struct e1000_adapter *adapter,
         i = rx_ring->next_to_clean;
         rx_desc = E1000_RX_DESC_PS(*rx_ring, i);
         staterr = le32_to_cpu(rx_desc->wb.middle.status_error);
-        buffer_info = &rx_ring->buffer_info[i];
 
         while (staterr & E1000_RXD_STAT_DD) {
+                buffer_info = &rx_ring->buffer_info[i];
                 ps_page = &rx_ring->ps_page[i];
                 ps_page_dma = &rx_ring->ps_page_dma[i];
 #ifdef CONFIG_E1000_NAPI
@@ -3722,10 +3728,16 @@ e1000_clean_rx_irq_ps(struct e1000_adapter *adapter,
 #endif
                 skb = buffer_info->skb;
 
+                /* in the packet split case this is header only */
+                prefetch(skb->data - NET_IP_ALIGN);
+
                 if (++i == rx_ring->count) i = 0;
                 next_rxd = E1000_RX_DESC_PS(*rx_ring, i);
+                prefetch(next_rxd);
+
                 next_buffer = &rx_ring->buffer_info[i];
                 next_skb = next_buffer->skb;
+                prefetch(next_skb->data - NET_IP_ALIGN);
 
                 cleaned = TRUE;
                 cleaned_count++;
@@ -3787,9 +3799,8 @@ e1000_clean_rx_irq_ps(struct e1000_adapter *adapter,
                 }
                 
                 for (j = 0; j < adapter->rx_ps_pages; j++) {
-                        if (!(length = le16_to_cpu(rx_desc->wb.upper.length[j])))
+                        if (!(length= le16_to_cpu(rx_desc->wb.upper.length[j])))
                                 break;
-
                         pci_unmap_page(pdev, ps_page_dma->ps_page_dma[j],
                                         PAGE_SIZE, PCI_DMA_FROMDEVICE);
                         ps_page_dma->ps_page_dma[j] = 0;
@@ -3837,6 +3848,7 @@ next_desc:
                         cleaned_count = 0;
                 }
 
+                /* use prefetched values */
                 rx_desc = next_rxd;
                 buffer_info = next_buffer;