Commit c8a8ca34 authored by Cristian Dumitrescu's avatar Cristian Dumitrescu Committed by Tony Nguyen
Browse files

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: default avatarCristian Dumitrescu <cristian.dumitrescu@intel.com>
Tested-by: default avatarKiran Bhandare <kiranx.bhandare@intel.com>
Signed-off-by: default avatarTony Nguyen <anthony.l.nguyen@intel.com>
parent 08cbabb7

drivers/net/ethernet/intel/i40e/i40e_xsk.c

+11 −19
Original line number Diff line number Diff line
@@ -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);