ixgb: add performance enhancements to the buffer_info struct

o modify the rx refill logic and tail bump
o add counter for failures

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Auke Kok <auke-jan.h.kok@intel.com>
Signed-off-by: John Ronciak <john.ronciak@intel.com>

2 files changed, 45 insertions, 30 deletions

diff --git a/drivers/net/ixgb/ixgb.h b/drivers/net/ixgb/ixgb.h
index b9c37fdc8418..bdbaf5acccee 100644
--- a/drivers/net/ixgb/ixgb.h
+++ b/drivers/net/ixgb/ixgb.h
@@ -200,6 +200,7 @@ struct ixgb_adapter {
         struct ixgb_hw hw;
         u16 msg_enable;
         struct ixgb_hw_stats stats;
+        uint32_t alloc_rx_buff_failed;
 #ifdef CONFIG_PCI_MSI
         boolean_t have_msi;
 #endif
diff --git a/drivers/net/ixgb/ixgb_main.c b/drivers/net/ixgb/ixgb_main.c
index 0905a8240939..27034b3ba80b 100644
--- a/drivers/net/ixgb/ixgb_main.c
+++ b/drivers/net/ixgb/ixgb_main.c
@@ -929,17 +929,20 @@ ixgb_unmap_and_free_tx_resource(struct ixgb_adapter *adapter,
                                         struct ixgb_buffer *buffer_info)
 {
         struct pci_dev *pdev = adapter->pdev;
-        if(buffer_info->dma) {
-                pci_unmap_page(pdev,
-                           buffer_info->dma,
-                           buffer_info->length,
-                           PCI_DMA_TODEVICE);
-                buffer_info->dma = 0;
-        }
-        if(buffer_info->skb) {
+
+        if (buffer_info->dma)
+                pci_unmap_page(pdev, buffer_info->dma, buffer_info->length,
+                               PCI_DMA_TODEVICE);
+
+        if (buffer_info->skb)
                 dev_kfree_skb_any(buffer_info->skb);
-                buffer_info->skb = NULL;
-        }
+
+        buffer_info->skb = NULL;
+        buffer_info->dma = 0;
+        buffer_info->time_stamp = 0;
+        /* these fields must always be initialized in tx
+         * buffer_info->length = 0;
+         * buffer_info->next_to_watch = 0; */
 }
 
 /**
@@ -1314,6 +1317,7 @@ ixgb_tx_map(struct ixgb_adapter *adapter, struct sk_buff *skb,
                                 size,
                                 PCI_DMA_TODEVICE);
                 buffer_info->time_stamp = jiffies;
+                buffer_info->next_to_watch = 0;
 
                 len -= size;
                 offset += size;
@@ -1345,6 +1349,7 @@ ixgb_tx_map(struct ixgb_adapter *adapter, struct sk_buff *skb,
                                         size,
                                         PCI_DMA_TODEVICE);
                         buffer_info->time_stamp = jiffies;
+                        buffer_info->next_to_watch = 0;
 
                         len -= size;
                         offset += size;
@@ -1940,6 +1945,7 @@ ixgb_clean_rx_irq(struct ixgb_adapter *adapter)
 #endif
                 status = rx_desc->status;
                 skb = buffer_info->skb;
+                buffer_info->skb = NULL;
 
                 prefetch(skb->data);
 
@@ -2013,7 +2019,6 @@ ixgb_clean_rx_irq(struct ixgb_adapter *adapter)
 rxdesc_done:
                 /* clean up descriptor, might be written over by hw */
                 rx_desc->status = 0;
-                buffer_info->skb = NULL;
 
                 /* use prefetched values */
                 rx_desc = next_rxd;
@@ -2053,12 +2058,18 @@ ixgb_alloc_rx_buffers(struct ixgb_adapter *adapter)
 
         /* leave three descriptors unused */
         while(--cleancount > 2) {
-                rx_desc = IXGB_RX_DESC(*rx_ring, i);
-
-                skb = dev_alloc_skb(adapter->rx_buffer_len + NET_IP_ALIGN);
+                /* recycle! its good for you */
+                if (!(skb = buffer_info->skb))
+                        skb = dev_alloc_skb(adapter->rx_buffer_len
+                                            + NET_IP_ALIGN);
+                else {
+                        skb_trim(skb, 0);
+                        goto map_skb;
+                }
 
-                if(unlikely(!skb)) {
+                if (unlikely(!skb)) {
                         /* Better luck next round */
+                        adapter->alloc_rx_buff_failed++;
                         break;
                 }
 
@@ -2072,33 +2083,36 @@ ixgb_alloc_rx_buffers(struct ixgb_adapter *adapter)
 
                 buffer_info->skb = skb;
                 buffer_info->length = adapter->rx_buffer_len;
-                buffer_info->dma =
-                        pci_map_single(pdev,
-                                   skb->data,
-                                   adapter->rx_buffer_len,
-                                   PCI_DMA_FROMDEVICE);
+map_skb:
+                buffer_info->dma = pci_map_single(pdev,
+                                                  skb->data,
+                                                  adapter->rx_buffer_len,
+                                                  PCI_DMA_FROMDEVICE);
 
+                rx_desc = IXGB_RX_DESC(*rx_ring, i);
                 rx_desc->buff_addr = cpu_to_le64(buffer_info->dma);
                 /* guarantee DD bit not set now before h/w gets descriptor
                  * this is the rest of the workaround for h/w double 
                  * writeback. */
                 rx_desc->status = 0;
 
-                if((i & ~(num_group_tail_writes- 1)) == i) {
-                        /* Force memory writes to complete before letting h/w
-                         * know there are new descriptors to fetch.  (Only
-                         * applicable for weak-ordered memory model archs,
-                         * such as IA-64). */
-                        wmb();
-
-                        IXGB_WRITE_REG(&adapter->hw, RDT, i);
-                }
 
                 if(++i == rx_ring->count) i = 0;
                 buffer_info = &rx_ring->buffer_info[i];
         }
 
-        rx_ring->next_to_use = i;
+        if (likely(rx_ring->next_to_use != i)) {
+                rx_ring->next_to_use = i;
+                if (unlikely(i-- == 0))
+                        i = (rx_ring->count - 1);
+
+                /* Force memory writes to complete before letting h/w
+                 * know there are new descriptors to fetch.  (Only
+                 * applicable for weak-ordered memory model archs, such
+                 * as IA-64). */
+                wmb();
+                IXGB_WRITE_REG(&adapter->hw, RDT, i);
+        }
 }
 
 /**