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Commit d57c0e08 authored by Alexander Duyck's avatar Alexander Duyck Committed by Jeff Kirsher
Browse files

i40e/i40evf: Use length to determine if descriptor is done 



This change makes it so that we use the length of the packet instead of the
DD status bit to determine if a new descriptor is ready to be processed.
The obvious advantage is that it cuts down on reads as we don't really even
need the DD bit if going from a 0 to a non-zero value on size is enough to
inform us that the packet has been completed.

Change-ID: Iebdf9cdb36c454ef092df27199b92ad09c374231
Signed-off-by: default avatarAlexander Duyck <alexander.h.duyck@intel.com>
Tested-by: default avatarAndrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: default avatarJeff Kirsher <jeffrey.t.kirsher@intel.com>
parent 3a104f8d

drivers/net/ethernet/intel/i40e/i40e_txrx.c

+12 −12
Original line number Diff line number Diff line
@@ -1757,6 +1757,7 @@ static bool i40e_add_rx_frag(struct i40e_ring *rx_ring, 
 * i40e_fetch_rx_buffer - Allocate skb and populate it

 * @rx_ring: rx descriptor ring to transact packets on

 * @rx_desc: descriptor containing info written by hardware

 * @size: size of buffer to add to skb

 *

 * This function allocates an skb on the fly, and populates it with the page

 * data from the current receive descriptor, taking care to set up the skb
@@ -1766,13 +1767,9 @@ static bool i40e_add_rx_frag(struct i40e_ring *rx_ring, 
static inline

struct sk_buff *i40e_fetch_rx_buffer(struct i40e_ring *rx_ring,

				     union i40e_rx_desc *rx_desc,

				     struct sk_buff *skb)

				     struct sk_buff *skb,

				     unsigned int size)

{

	u64 local_status_error_len =

		le64_to_cpu(rx_desc->wb.qword1.status_error_len);

	unsigned int size =

		(local_status_error_len & I40E_RXD_QW1_LENGTH_PBUF_MASK) >>

		I40E_RXD_QW1_LENGTH_PBUF_SHIFT;

	struct i40e_rx_buffer *rx_buffer;

	struct page *page;
@@ -1890,6 +1887,7 @@ static int i40e_clean_rx_irq(struct i40e_ring *rx_ring, int budget) 


	while (likely(total_rx_packets < budget)) {

		union i40e_rx_desc *rx_desc;

		unsigned int size;

		u16 vlan_tag;

		u8 rx_ptype;

		u64 qword;
@@ -1906,19 +1904,21 @@ static int i40e_clean_rx_irq(struct i40e_ring *rx_ring, int budget) 
		/* status_error_len will always be zero for unused descriptors

		 * because it's cleared in cleanup, and overlaps with hdr_addr

		 * which is always zero because packet split isn't used, if the

		 * hardware wrote DD then it will be non-zero

		 * hardware wrote DD then the length will be non-zero

		 */

		if (!i40e_test_staterr(rx_desc,

				       BIT(I40E_RX_DESC_STATUS_DD_SHIFT)))

		qword = le64_to_cpu(rx_desc->wb.qword1.status_error_len);

		size = (qword & I40E_RXD_QW1_LENGTH_PBUF_MASK) >>

		       I40E_RXD_QW1_LENGTH_PBUF_SHIFT;

		if (!size)

			break;



		/* This memory barrier is needed to keep us from reading

		 * any other fields out of the rx_desc until we know the

		 * DD bit is set.

		 * any other fields out of the rx_desc until we have

		 * verified the descriptor has been written back.

		 */

		dma_rmb();



		skb = i40e_fetch_rx_buffer(rx_ring, rx_desc, skb);

		skb = i40e_fetch_rx_buffer(rx_ring, rx_desc, skb, size);

		if (!skb)

			break;

drivers/net/ethernet/intel/i40evf/i40e_txrx.c

+12 −12
Original line number Diff line number Diff line
@@ -1116,6 +1116,7 @@ static bool i40e_add_rx_frag(struct i40e_ring *rx_ring, 
 * i40evf_fetch_rx_buffer - Allocate skb and populate it

 * @rx_ring: rx descriptor ring to transact packets on

 * @rx_desc: descriptor containing info written by hardware

 * @size: size of buffer to add to skb

 *

 * This function allocates an skb on the fly, and populates it with the page

 * data from the current receive descriptor, taking care to set up the skb
@@ -1125,13 +1126,9 @@ static bool i40e_add_rx_frag(struct i40e_ring *rx_ring, 
static inline

struct sk_buff *i40evf_fetch_rx_buffer(struct i40e_ring *rx_ring,

				       union i40e_rx_desc *rx_desc,

				       struct sk_buff *skb)

				       struct sk_buff *skb,

				       unsigned int size)

{

	u64 local_status_error_len =

		le64_to_cpu(rx_desc->wb.qword1.status_error_len);

	unsigned int size =

		(local_status_error_len & I40E_RXD_QW1_LENGTH_PBUF_MASK) >>

		I40E_RXD_QW1_LENGTH_PBUF_SHIFT;

	struct i40e_rx_buffer *rx_buffer;

	struct page *page;
@@ -1244,6 +1241,7 @@ static int i40e_clean_rx_irq(struct i40e_ring *rx_ring, int budget) 


	while (likely(total_rx_packets < budget)) {

		union i40e_rx_desc *rx_desc;

		unsigned int size;

		u16 vlan_tag;

		u8 rx_ptype;

		u64 qword;
@@ -1260,19 +1258,21 @@ static int i40e_clean_rx_irq(struct i40e_ring *rx_ring, int budget) 
		/* status_error_len will always be zero for unused descriptors

		 * because it's cleared in cleanup, and overlaps with hdr_addr

		 * which is always zero because packet split isn't used, if the

		 * hardware wrote DD then it will be non-zero

		 * hardware wrote DD then the length will be non-zero

		 */

		if (!i40e_test_staterr(rx_desc,

				       BIT(I40E_RX_DESC_STATUS_DD_SHIFT)))

		qword = le64_to_cpu(rx_desc->wb.qword1.status_error_len);

		size = (qword & I40E_RXD_QW1_LENGTH_PBUF_MASK) >>

		       I40E_RXD_QW1_LENGTH_PBUF_SHIFT;

		if (!size)

			break;



		/* This memory barrier is needed to keep us from reading

		 * any other fields out of the rx_desc until we know the

		 * DD bit is set.

		 * any other fields out of the rx_desc until we have

		 * verified the descriptor has been written back.

		 */

		dma_rmb();



		skb = i40evf_fetch_rx_buffer(rx_ring, rx_desc, skb);

		skb = i40evf_fetch_rx_buffer(rx_ring, rx_desc, skb, size);

		if (!skb)

			break;