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igb: Make first and tx_buffer_info->next_to_watch into pointers
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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>
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Alexander Duyck authored and Jeff Kirsher committed Oct 7, 2011
1 parent 7d13a7d commit 8542db0
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Showing 2 changed files with 37 additions and 31 deletions.
2 changes: 1 addition & 1 deletion drivers/net/ethernet/intel/igb/igb.h
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Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down
66 changes: 36 additions & 30 deletions drivers/net/ethernet/intel/igb/igb_main.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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,
Expand Down Expand Up @@ -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,
Expand Down Expand Up @@ -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;
}

Expand Down Expand Up @@ -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;
Expand All @@ -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))
Expand All @@ -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);
Expand All @@ -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;

Expand All @@ -4165,7 +4167,6 @@ static inline int igb_tx_map(struct igb_ring *tx_ring, struct sk_buff *skb,
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 */
Expand Down Expand Up @@ -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,
Expand All @@ -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);

Expand All @@ -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;
}

Expand Down Expand Up @@ -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;
Expand All @@ -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;
Expand All @@ -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)) {

Expand All @@ -5648,16 +5654,16 @@ 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,
rd32(E1000_TDH(tx_ring->reg_idx)),
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,
Expand Down

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