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i40e: remove unnecessary memory writes of the next to clean pointer 

For performance reasons, avoid writing the ring next-to-clean pointer
value back to memory on every update, as it is not really necessary.
Instead, simply read it at initialization into a local copy, update
the local copy as necessary and write the local copy back to memory
after the last update.

Signed-off-by: Cristian Dumitrescu <cristian.dumitrescu@intel.com>
Tested-by: Kiran Bhandare <kiranx.bhandare@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
This commit is contained in:
Cristian Dumitrescu 2021-01-14 14:33:15 +00:00 committed by Tony Nguyen
parent 08cbabb77e
commit c8a8ca3408
1 changed files with 11 additions and 19 deletions
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30
drivers/net/ethernet/intel/i40e/i40e_xsk.c
View File

@ -261,18 +261,6 @@ static struct sk_buff *i40e_construct_skb_zc(struct i40e_ring *rx_ring,
return skb;
}
/**
* i40e_inc_ntc: Advance the next_to_clean index
* @rx_ring: Rx ring
**/
static void i40e_inc_ntc(struct i40e_ring *rx_ring)
{
u32 ntc = rx_ring->next_to_clean + 1;
ntc = (ntc < rx_ring->count) ? ntc : 0;
rx_ring->next_to_clean = ntc;
}
/**
* i40e_clean_rx_irq_zc - Consumes Rx packets from the hardware ring
* @rx_ring: Rx ring
@ -284,6 +272,8 @@ int i40e_clean_rx_irq_zc(struct i40e_ring *rx_ring, int budget)
{
unsigned int total_rx_bytes = 0, total_rx_packets = 0;
u16 cleaned_count = I40E_DESC_UNUSED(rx_ring);
u16 next_to_clean = rx_ring->next_to_clean;
u16 count_mask = rx_ring->count - 1;
unsigned int xdp_res, xdp_xmit = 0;
bool failure = false;
struct sk_buff *skb;
@ -294,7 +284,7 @@ int i40e_clean_rx_irq_zc(struct i40e_ring *rx_ring, int budget)
unsigned int size;
u64 qword;
rx_desc = I40E_RX_DESC(rx_ring, rx_ring->next_to_clean);
rx_desc = I40E_RX_DESC(rx_ring, next_to_clean);
qword = le64_to_cpu(rx_desc->wb.qword1.status_error_len);
/* This memory barrier is needed to keep us from reading
@ -307,11 +297,11 @@ int i40e_clean_rx_irq_zc(struct i40e_ring *rx_ring, int budget)
i40e_clean_programming_status(rx_ring,
rx_desc->raw.qword[0],
qword);
bi = i40e_rx_bi(rx_ring, rx_ring->next_to_clean);
bi = i40e_rx_bi(rx_ring, next_to_clean);
xsk_buff_free(*bi);
*bi = NULL;
cleaned_count++;
i40e_inc_ntc(rx_ring);
next_to_clean = (next_to_clean + 1) & count_mask;
continue;
}
@ -320,7 +310,7 @@ int i40e_clean_rx_irq_zc(struct i40e_ring *rx_ring, int budget)
if (!size)
break;
bi = i40e_rx_bi(rx_ring, rx_ring->next_to_clean);
bi = i40e_rx_bi(rx_ring, next_to_clean);
(*bi)->data_end = (*bi)->data + size;
xsk_buff_dma_sync_for_cpu(*bi, rx_ring->xsk_pool);
@ -336,7 +326,7 @@ int i40e_clean_rx_irq_zc(struct i40e_ring *rx_ring, int budget)
total_rx_packets++;
cleaned_count++;
i40e_inc_ntc(rx_ring);
next_to_clean = (next_to_clean + 1) & count_mask;
continue;
}
@ -355,7 +345,7 @@ int i40e_clean_rx_irq_zc(struct i40e_ring *rx_ring, int budget)
*bi = NULL;
cleaned_count++;
i40e_inc_ntc(rx_ring);
next_to_clean = (next_to_clean + 1) & count_mask;
if (eth_skb_pad(skb))
continue;
@ -367,6 +357,8 @@ int i40e_clean_rx_irq_zc(struct i40e_ring *rx_ring, int budget)
napi_gro_receive(&rx_ring->q_vector->napi, skb);
}
rx_ring->next_to_clean = next_to_clean;
if (cleaned_count >= I40E_RX_BUFFER_WRITE)
failure = !i40e_alloc_rx_buffers_zc(rx_ring, cleaned_count);
@ -374,7 +366,7 @@ int i40e_clean_rx_irq_zc(struct i40e_ring *rx_ring, int budget)
i40e_update_rx_stats(rx_ring, total_rx_bytes, total_rx_packets);
if (xsk_uses_need_wakeup(rx_ring->xsk_pool)) {
if (failure || rx_ring->next_to_clean == rx_ring->next_to_use)
if (failure || next_to_clean == rx_ring->next_to_use)
xsk_set_rx_need_wakeup(rx_ring->xsk_pool);
else
xsk_clear_rx_need_wakeup(rx_ring->xsk_pool);