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i40e/i40evf: Use length to determine if descriptor is done
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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: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
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Alexander Duyck authored and Jeff Kirsher committed Mar 29, 2017
1 parent 3a104f8 commit d57c0e0
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Showing 2 changed files with 24 additions and 24 deletions.
24 changes: 12 additions & 12 deletions drivers/net/ethernet/intel/i40e/i40e_txrx.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand All @@ -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;

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

Expand Down
24 changes: 12 additions & 12 deletions drivers/net/ethernet/intel/i40evf/i40e_txrx.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand All @@ -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;

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

Expand Down

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