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Commit 0e014cb1 authored by Alexander Duyck's avatar Alexander Duyck Committed by David S. Miller
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igb: defeature tx head writeback 



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: default avatarAlexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: default avatarJeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent f2712fd0

drivers/net/igb/e1000_defines.h

+1 −0
Original line number Diff line number Diff line
@@ -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 */

drivers/net/igb/igb.h

+2 −3
Original line number Diff line number Diff line
@@ -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
@@ -127,7 +125,8 @@ struct igb_buffer { 
		/* TX */

		struct {

			unsigned long time_stamp;

			u32 length;

			u16 length;

			u16 next_to_watch;

		};

		/* RX */

		struct {

drivers/net/igb/igb_main.c

+36 −49
Original line number Diff line number Diff line
@@ -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,
@@ -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;
@@ -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);
@@ -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)
@@ -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++;
@@ -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);
@@ -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++;
@@ -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,
@@ -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;

}
@@ -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;
@@ -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;
@@ -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;
@@ -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
@@ -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) {
@@ -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;

		}



		eop = tx_ring->buffer_info[i].next_to_watch;

		eop_desc = E1000_TX_DESC_ADV(*tx_ring, eop);

	}

		oldhead = head;

		rmb();

		head = get_head(tx_ring);

		if (head == oldhead)

			goto done_cleaning;

	}  /* while (1) */



done_cleaning:

	tx_ring->next_to_clean = i;



	if (unlikely(count &&
@@ -3708,7 +3696,6 @@ done_cleaning: 
		    && !(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"
@@ -3717,9 +3704,9 @@ done_cleaning: 
				"  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,
@@ -3727,10 +3714,10 @@ done_cleaning: 
				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);

		}

	}
@@ -3740,7 +3727,7 @@ done_cleaning: 
	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