igb: Make first and tx_buffer_info->next_to_watch into pointers

This change converts two tx_buffer_info index values into pointers.  The
advantage to this is that we reduce unnecessary computations and in the case
of next_to_watch we get an added bonus of the value being able to provide
additional information as a NULL value indicates it is unset versus a 0 not
having any meaning for the index value.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by:  Aaron Brown  <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

diff --git a/drivers/net/ethernet/intel/igb/igb.h b/drivers/net/ethernet/intel/igb/igb.h
index 56c68fc..7185667 100644 (file)
--- a/drivers/net/ethernet/intel/igb/igb.h
+++ b/drivers/net/ethernet/intel/igb/igb.h
@@ -133,7 +133,7 @@ struct vf_data_storage {
 /* wrapper around a pointer to a socket buffer,
  * so a DMA handle can be stored along with the buffer */
 struct igb_tx_buffer {
-       u16 next_to_watch;
+       union e1000_adv_tx_desc *next_to_watch;
        unsigned long time_stamp;
        dma_addr_t dma;
        u32 length;

diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index a0bb81d..edc2cae 100644 (file)
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -381,7 +381,7 @@ static void igb_dump(struct igb_adapter *adapter)
                struct igb_tx_buffer *buffer_info;
                tx_ring = adapter->tx_ring[n];
                buffer_info = &tx_ring->tx_buffer_info[tx_ring->next_to_clean];
-               printk(KERN_INFO " %5d %5X %5X %016llX %04X %3X %016llX\n",
+               printk(KERN_INFO " %5d %5X %5X %016llX %04X %p %016llX\n",
                           n, tx_ring->next_to_use, tx_ring->next_to_clean,
                           (u64)buffer_info->dma,
                           buffer_info->length,
@@ -421,7 +421,7 @@ static void igb_dump(struct igb_adapter *adapter)
                        buffer_info = &tx_ring->tx_buffer_info[i];
                        u0 = (struct my_u0 *)tx_desc;
                        printk(KERN_INFO "T [0x%03X]    %016llX %016llX %016llX"
-                               " %04X  %3X %016llX %p", i,
+                               " %04X  %p %016llX %p", i,
                                le64_to_cpu(u0->a),
                                le64_to_cpu(u0->b),
                                (u64)buffer_info->dma,
@@ -3161,7 +3161,7 @@ void igb_unmap_and_free_tx_resource(struct igb_ring *tx_ring,
        }
        buffer_info->time_stamp = 0;
        buffer_info->length = 0;
-       buffer_info->next_to_watch = 0;
+       buffer_info->next_to_watch = NULL;
        buffer_info->mapped_as_page = false;
 }
 
@@ -4107,7 +4107,7 @@ static inline bool igb_tx_csum(struct igb_ring *tx_ring,
 #define IGB_MAX_DATA_PER_TXD   (1<<IGB_MAX_TXD_PWR)
 
 static inline int igb_tx_map(struct igb_ring *tx_ring, struct sk_buff *skb,
-                            unsigned int first)
+                            struct igb_tx_buffer *first)
 {
        struct igb_tx_buffer *buffer_info;
        struct device *dev = tx_ring->dev;
@@ -4121,7 +4121,6 @@ static inline int igb_tx_map(struct igb_ring *tx_ring, struct sk_buff *skb,
        buffer_info = &tx_ring->tx_buffer_info[i];
        BUG_ON(hlen >= IGB_MAX_DATA_PER_TXD);
        buffer_info->length = hlen;
-       buffer_info->next_to_watch = i;
        buffer_info->dma = dma_map_single(dev, skb->data, hlen,
                                          DMA_TO_DEVICE);
        if (dma_mapping_error(dev, buffer_info->dma))
@@ -4139,7 +4138,6 @@ static inline int igb_tx_map(struct igb_ring *tx_ring, struct sk_buff *skb,
                buffer_info = &tx_ring->tx_buffer_info[i];
                BUG_ON(len >= IGB_MAX_DATA_PER_TXD);
                buffer_info->length = len;
-               buffer_info->next_to_watch = i;
                buffer_info->mapped_as_page = true;
                buffer_info->dma = skb_frag_dma_map(dev, frag, 0, len,
                                                DMA_TO_DEVICE);
@@ -4153,8 +4151,12 @@ static inline int igb_tx_map(struct igb_ring *tx_ring, struct sk_buff *skb,
        /* multiply data chunks by size of headers */
        buffer_info->bytecount = ((gso_segs - 1) * hlen) + skb->len;
        buffer_info->gso_segs = gso_segs;
-       tx_ring->tx_buffer_info[first].next_to_watch = i;
-       tx_ring->tx_buffer_info[first].time_stamp = jiffies;
+
+       /* set the timestamp */
+       first->time_stamp = jiffies;
+
+       /* set next_to_watch value indicating a packet is present */
+       first->next_to_watch = IGB_TX_DESC(tx_ring, i);
 
        return ++count;
 
@@ -4165,7 +4167,6 @@ dma_error:
        buffer_info->dma = 0;
        buffer_info->time_stamp = 0;
        buffer_info->length = 0;
-       buffer_info->next_to_watch = 0;
        buffer_info->mapped_as_page = false;
 
        /* clear timestamp and dma mappings for remaining portion of packet */
@@ -4283,9 +4284,9 @@ static inline int igb_maybe_stop_tx(struct igb_ring *tx_ring, int size)
 netdev_tx_t igb_xmit_frame_ring(struct sk_buff *skb,
                                struct igb_ring *tx_ring)
 {
+       struct igb_tx_buffer *first;
        int tso, count;
        u32 tx_flags = 0;
-       u16 first;
        u8 hdr_len = 0;
 
        /* need: 1 descriptor per page,
@@ -4311,7 +4312,8 @@ netdev_tx_t igb_xmit_frame_ring(struct sk_buff *skb,
        if (skb->protocol == htons(ETH_P_IP))
                tx_flags |= IGB_TX_FLAGS_IPV4;
 
-       first = tx_ring->next_to_use;
+       /* record the location of the first descriptor for this packet */
+       first = &tx_ring->tx_buffer_info[tx_ring->next_to_use];
 
        tso = igb_tso(tx_ring, skb, tx_flags, &hdr_len);
 
@@ -4330,8 +4332,8 @@ netdev_tx_t igb_xmit_frame_ring(struct sk_buff *skb,
        count = igb_tx_map(tx_ring, skb, first);
        if (!count) {
                dev_kfree_skb_any(skb);
-               tx_ring->tx_buffer_info[first].time_stamp = 0;
-               tx_ring->next_to_use = first;
+               first->time_stamp = 0;
+               tx_ring->next_to_use = first - tx_ring->tx_buffer_info;
                return NETDEV_TX_OK;
        }
 
@@ -5568,29 +5570,34 @@ static bool igb_clean_tx_irq(struct igb_q_vector *q_vector)
        struct igb_adapter *adapter = q_vector->adapter;
        struct igb_ring *tx_ring = q_vector->tx_ring;
        struct igb_tx_buffer *tx_buffer;
-       union e1000_adv_tx_desc *tx_desc;
+       union e1000_adv_tx_desc *tx_desc, *eop_desc;
        unsigned int total_bytes = 0, total_packets = 0;
        unsigned int budget = q_vector->tx_work_limit;
-       u16 i = tx_ring->next_to_clean;
+       unsigned int i = tx_ring->next_to_clean;
 
        if (test_bit(__IGB_DOWN, &adapter->state))
                return true;
 
        tx_buffer = &tx_ring->tx_buffer_info[i];
        tx_desc = IGB_TX_DESC(tx_ring, i);
+       i -= tx_ring->count;
 
        for (; budget; budget--) {
-               u16 eop = tx_buffer->next_to_watch;
-               union e1000_adv_tx_desc *eop_desc;
+               eop_desc = tx_buffer->next_to_watch;
 
-               eop_desc = IGB_TX_DESC(tx_ring, eop);
+               /* prevent any other reads prior to eop_desc */
+               rmb();
+
+               /* if next_to_watch is not set then there is no work pending */
+               if (!eop_desc)
+                       break;
 
                /* if DD is not set pending work has not been completed */
                if (!(eop_desc->wb.status & cpu_to_le32(E1000_TXD_STAT_DD)))
                        break;
 
-               /* prevent any other reads prior to eop_desc being verified */
-               rmb();
+               /* clear next_to_watch to prevent false hangs */
+               tx_buffer->next_to_watch = NULL;
 
                do {
                        tx_desc->wb.status = 0;
@@ -5607,14 +5614,15 @@ static bool igb_clean_tx_irq(struct igb_q_vector *q_vector)
                        tx_buffer++;
                        tx_desc++;
                        i++;
-                       if (unlikely(i == tx_ring->count)) {
-                               i = 0;
+                       if (unlikely(!i)) {
+                               i -= tx_ring->count;
                                tx_buffer = tx_ring->tx_buffer_info;
                                tx_desc = IGB_TX_DESC(tx_ring, 0);
                        }
                } while (eop_desc);
        }
 
+       i += tx_ring->count;
        tx_ring->next_to_clean = i;
        u64_stats_update_begin(&tx_ring->tx_syncp);
        tx_ring->tx_stats.bytes += total_bytes;
@@ -5625,16 +5633,14 @@ static bool igb_clean_tx_irq(struct igb_q_vector *q_vector)
 
        if (tx_ring->detect_tx_hung) {
                struct e1000_hw *hw = &adapter->hw;
-               u16 eop = tx_ring->tx_buffer_info[i].next_to_watch;
-               union e1000_adv_tx_desc *eop_desc;
 
-               eop_desc = IGB_TX_DESC(tx_ring, eop);
+               eop_desc = tx_buffer->next_to_watch;
 
                /* Detect a transmit hang in hardware, this serializes the
                 * check with the clearing of time_stamp and movement of i */
                tx_ring->detect_tx_hung = false;
-               if (tx_ring->tx_buffer_info[i].time_stamp &&
-                   time_after(jiffies, tx_ring->tx_buffer_info[i].time_stamp +
+               if (eop_desc &&
+                   time_after(jiffies, tx_buffer->time_stamp +
                               (adapter->tx_timeout_factor * HZ)) &&
                    !(rd32(E1000_STATUS) & E1000_STATUS_TXOFF)) {
 
@@ -5648,7 +5654,7 @@ static bool igb_clean_tx_irq(struct igb_q_vector *q_vector)
                                "  next_to_clean        <%x>\n"
                                "buffer_info[next_to_clean]\n"
                                "  time_stamp           <%lx>\n"
-                               "  next_to_watch        <%x>\n"
+                               "  next_to_watch        <%p>\n"
                                "  jiffies              <%lx>\n"
                                "  desc.status          <%x>\n",
                                tx_ring->queue_index,
@@ -5656,8 +5662,8 @@ static bool igb_clean_tx_irq(struct igb_q_vector *q_vector)
                                readl(tx_ring->tail),
                                tx_ring->next_to_use,
                                tx_ring->next_to_clean,
-                               tx_ring->tx_buffer_info[eop].time_stamp,
-                               eop,
+                               tx_buffer->time_stamp,
+                               eop_desc,
                                jiffies,
                                eop_desc->wb.status);
                        netif_stop_subqueue(tx_ring->netdev,