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>

diff --git a/drivers/net/e1000/e1000_main.c b/drivers/net/e1000/e1000_main.c
index d641fbc7a6e168d34736094dc5f31996a98e7a73..b572a1218c819ac7508738fa173bc93e7a5f4872 100644 (file)
--- 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;