[PATCH net-next 1/6] i40e: remove unnecessary memory writes of the next to clean pointer
From: Tony Nguyen <anthony.l.nguyen@intel.com>
Date: 2021-02-02 02:24:31
Subsystem:
intel ethernet drivers, networking drivers, the rest · Maintainers:
Tony Nguyen, Przemek Kitszel, Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
From: Cristian Dumitrescu <redacted> 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 <redacted> Tested-by: Kiran Bhandare <redacted> Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com> --- drivers/net/ethernet/intel/i40e/i40e_xsk.c | 30 ++++++++-------------- 1 file changed, 11 insertions(+), 19 deletions(-)
diff --git a/drivers/net/ethernet/intel/i40e/i40e_xsk.c b/drivers/net/ethernet/intel/i40e/i40e_xsk.c
index 492ce213208d..87d43407653c 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_xsk.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_xsk.c@@ -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);
--
2.26.2