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igb: defeature tx head writeback
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This patch removes tx head writeback as it was found to not provide a
significant improvement in tx performance and on some systems has been seen
to cause a performance degredation due to partial cache line writes.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Alexander Duyck authored and David S. Miller committed Dec 26, 2008
1 parent f2712fd commit 0e014cb
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Showing 3 changed files with 39 additions and 52 deletions.
1 change: 1 addition & 0 deletions drivers/net/igb/e1000_defines.h
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Original file line number Diff line number Diff line change
Expand Up @@ -323,6 +323,7 @@
#define E1000_TXD_CMD_IFCS 0x02000000 /* Insert FCS (Ethernet CRC) */
#define E1000_TXD_CMD_RS 0x08000000 /* Report Status */
#define E1000_TXD_CMD_DEXT 0x20000000 /* Descriptor extension (0 = legacy) */
#define E1000_TXD_STAT_DD 0x00000001 /* Descriptor Done */
/* Extended desc bits for Linksec and timesync */

/* Transmit Control */
Expand Down
5 changes: 2 additions & 3 deletions drivers/net/igb/igb.h
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Original file line number Diff line number Diff line change
Expand Up @@ -43,8 +43,6 @@ struct igb_adapter;
#endif

/* Interrupt defines */
#define IGB_MAX_TX_CLEAN 72

#define IGB_MIN_DYN_ITR 3000
#define IGB_MAX_DYN_ITR 96000

Expand Down Expand Up @@ -127,7 +125,8 @@ struct igb_buffer {
/* TX */
struct {
unsigned long time_stamp;
u32 length;
u16 length;
u16 next_to_watch;
};
/* RX */
struct {
Expand Down
85 changes: 36 additions & 49 deletions drivers/net/igb/igb_main.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1575,8 +1575,7 @@ int igb_setup_tx_resources(struct igb_adapter *adapter,
memset(tx_ring->buffer_info, 0, size);

/* round up to nearest 4K */
tx_ring->size = tx_ring->count * sizeof(struct e1000_tx_desc)
+ sizeof(u32);
tx_ring->size = tx_ring->count * sizeof(struct e1000_tx_desc);
tx_ring->size = ALIGN(tx_ring->size, 4096);

tx_ring->desc = pci_alloc_consistent(pdev, tx_ring->size,
Expand Down Expand Up @@ -1635,7 +1634,7 @@ static int igb_setup_all_tx_resources(struct igb_adapter *adapter)
**/
static void igb_configure_tx(struct igb_adapter *adapter)
{
u64 tdba, tdwba;
u64 tdba;
struct e1000_hw *hw = &adapter->hw;
u32 tctl;
u32 txdctl, txctrl;
Expand All @@ -1651,12 +1650,6 @@ static void igb_configure_tx(struct igb_adapter *adapter)
tdba & 0x00000000ffffffffULL);
wr32(E1000_TDBAH(i), tdba >> 32);

tdwba = ring->dma + ring->count * sizeof(struct e1000_tx_desc);
tdwba |= 1; /* enable head wb */
wr32(E1000_TDWBAL(i),
tdwba & 0x00000000ffffffffULL);
wr32(E1000_TDWBAH(i), tdwba >> 32);

ring->head = E1000_TDH(i);
ring->tail = E1000_TDT(i);
writel(0, hw->hw_addr + ring->tail);
Expand Down Expand Up @@ -2710,6 +2703,7 @@ static inline int igb_tso_adv(struct igb_adapter *adapter,
context_desc->seqnum_seed = 0;

buffer_info->time_stamp = jiffies;
buffer_info->next_to_watch = i;
buffer_info->dma = 0;
i++;
if (i == tx_ring->count)
Expand Down Expand Up @@ -2773,6 +2767,7 @@ static inline bool igb_tx_csum_adv(struct igb_adapter *adapter,
cpu_to_le32(tx_ring->queue_index << 4);

buffer_info->time_stamp = jiffies;
buffer_info->next_to_watch = i;
buffer_info->dma = 0;

i++;
Expand All @@ -2791,8 +2786,8 @@ static inline bool igb_tx_csum_adv(struct igb_adapter *adapter,
#define IGB_MAX_DATA_PER_TXD (1<<IGB_MAX_TXD_PWR)

static inline int igb_tx_map_adv(struct igb_adapter *adapter,
struct igb_ring *tx_ring,
struct sk_buff *skb)
struct igb_ring *tx_ring, struct sk_buff *skb,
unsigned int first)
{
struct igb_buffer *buffer_info;
unsigned int len = skb_headlen(skb);
Expand All @@ -2806,6 +2801,7 @@ static inline int igb_tx_map_adv(struct igb_adapter *adapter,
buffer_info->length = len;
/* set time_stamp *before* dma to help avoid a possible race */
buffer_info->time_stamp = jiffies;
buffer_info->next_to_watch = i;
buffer_info->dma = pci_map_single(adapter->pdev, skb->data, len,
PCI_DMA_TODEVICE);
count++;
Expand All @@ -2823,6 +2819,7 @@ static inline int igb_tx_map_adv(struct igb_adapter *adapter,
BUG_ON(len >= IGB_MAX_DATA_PER_TXD);
buffer_info->length = len;
buffer_info->time_stamp = jiffies;
buffer_info->next_to_watch = i;
buffer_info->dma = pci_map_page(adapter->pdev,
frag->page,
frag->page_offset,
Expand All @@ -2835,8 +2832,9 @@ static inline int igb_tx_map_adv(struct igb_adapter *adapter,
i = 0;
}

i = (i == 0) ? tx_ring->count - 1 : i - 1;
i = ((i == 0) ? tx_ring->count - 1 : i - 1);
tx_ring->buffer_info[i].skb = skb;
tx_ring->buffer_info[first].next_to_watch = i;

return count;
}
Expand Down Expand Up @@ -2943,6 +2941,7 @@ static int igb_xmit_frame_ring_adv(struct sk_buff *skb,
struct igb_ring *tx_ring)
{
struct igb_adapter *adapter = netdev_priv(netdev);
unsigned int first;
unsigned int tx_flags = 0;
unsigned int len;
u8 hdr_len = 0;
Expand Down Expand Up @@ -2979,6 +2978,8 @@ static int igb_xmit_frame_ring_adv(struct sk_buff *skb,
if (skb->protocol == htons(ETH_P_IP))
tx_flags |= IGB_TX_FLAGS_IPV4;

first = tx_ring->next_to_use;

tso = skb_is_gso(skb) ? igb_tso_adv(adapter, tx_ring, skb, tx_flags,
&hdr_len) : 0;

Expand All @@ -2994,7 +2995,7 @@ static int igb_xmit_frame_ring_adv(struct sk_buff *skb,
tx_flags |= IGB_TX_FLAGS_CSUM;

igb_tx_queue_adv(adapter, tx_ring, tx_flags,
igb_tx_map_adv(adapter, tx_ring, skb),
igb_tx_map_adv(adapter, tx_ring, skb, first),
skb->len, hdr_len);

netdev->trans_start = jiffies;
Expand Down Expand Up @@ -3617,12 +3618,6 @@ static int igb_clean_rx_ring_msix(struct napi_struct *napi, int budget)
return 1;
}

static inline u32 get_head(struct igb_ring *tx_ring)
{
void *end = (struct e1000_tx_desc *)tx_ring->desc + tx_ring->count;
return le32_to_cpu(*(volatile __le32 *)end);
}

/**
* igb_clean_tx_irq - Reclaim resources after transmit completes
* @adapter: board private structure
Expand All @@ -3631,24 +3626,25 @@ static inline u32 get_head(struct igb_ring *tx_ring)
static bool igb_clean_tx_irq(struct igb_ring *tx_ring)
{
struct igb_adapter *adapter = tx_ring->adapter;
struct e1000_hw *hw = &adapter->hw;
struct net_device *netdev = adapter->netdev;
struct e1000_tx_desc *tx_desc;
struct e1000_hw *hw = &adapter->hw;
struct igb_buffer *buffer_info;
struct sk_buff *skb;
unsigned int i;
u32 head, oldhead;
unsigned int count = 0;
union e1000_adv_tx_desc *tx_desc, *eop_desc;
unsigned int total_bytes = 0, total_packets = 0;
bool retval = true;
unsigned int i, eop, count = 0;
bool cleaned = false;

rmb();
head = get_head(tx_ring);
i = tx_ring->next_to_clean;
while (1) {
while (i != head) {
tx_desc = E1000_TX_DESC(*tx_ring, i);
eop = tx_ring->buffer_info[i].next_to_watch;
eop_desc = E1000_TX_DESC_ADV(*tx_ring, eop);

while ((eop_desc->wb.status & cpu_to_le32(E1000_TXD_STAT_DD)) &&
(count < tx_ring->count)) {
for (cleaned = false; !cleaned; count++) {
tx_desc = E1000_TX_DESC_ADV(*tx_ring, i);
buffer_info = &tx_ring->buffer_info[i];
cleaned = (i == eop);
skb = buffer_info->skb;

if (skb) {
Expand All @@ -3663,25 +3659,17 @@ static bool igb_clean_tx_irq(struct igb_ring *tx_ring)
}

igb_unmap_and_free_tx_resource(adapter, buffer_info);
tx_desc->wb.status = 0;

i++;
if (i == tx_ring->count)
i = 0;

count++;
if (count == IGB_MAX_TX_CLEAN) {
retval = false;
goto done_cleaning;
}
}
oldhead = head;
rmb();
head = get_head(tx_ring);
if (head == oldhead)
goto done_cleaning;
} /* while (1) */

done_cleaning:

eop = tx_ring->buffer_info[i].next_to_watch;
eop_desc = E1000_TX_DESC_ADV(*tx_ring, eop);
}

tx_ring->next_to_clean = i;

if (unlikely(count &&
Expand All @@ -3708,7 +3696,6 @@ static bool igb_clean_tx_irq(struct igb_ring *tx_ring)
&& !(rd32(E1000_STATUS) &
E1000_STATUS_TXOFF)) {

tx_desc = E1000_TX_DESC(*tx_ring, i);
/* detected Tx unit hang */
dev_err(&adapter->pdev->dev,
"Detected Tx Unit Hang\n"
Expand All @@ -3717,20 +3704,20 @@ static bool igb_clean_tx_irq(struct igb_ring *tx_ring)
" TDT <%x>\n"
" next_to_use <%x>\n"
" next_to_clean <%x>\n"
" head (WB) <%x>\n"
"buffer_info[next_to_clean]\n"
" time_stamp <%lx>\n"
" next_to_watch <%x>\n"
" jiffies <%lx>\n"
" desc.status <%x>\n",
tx_ring->queue_index,
readl(adapter->hw.hw_addr + tx_ring->head),
readl(adapter->hw.hw_addr + tx_ring->tail),
tx_ring->next_to_use,
tx_ring->next_to_clean,
head,
tx_ring->buffer_info[i].time_stamp,
eop,
jiffies,
tx_desc->upper.fields.status);
eop_desc->wb.status);
netif_stop_subqueue(netdev, tx_ring->queue_index);
}
}
Expand All @@ -3740,7 +3727,7 @@ static bool igb_clean_tx_irq(struct igb_ring *tx_ring)
tx_ring->tx_stats.packets += total_packets;
adapter->net_stats.tx_bytes += total_bytes;
adapter->net_stats.tx_packets += total_packets;
return retval;
return (count < tx_ring->count);
}

#ifdef CONFIG_IGB_LRO
Expand Down

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