netdev - [PATCH bpf-next 3/3] ice: xsk: borrow xdp_tx

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Date:   Fri, 10 Dec 2021 18:14:25 +0100
From:   Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To:     bpf@...r.kernel.org, ast@...nel.org, daniel@...earbox.net
Cc:     netdev@...r.kernel.org, magnus.karlsson@...el.com,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Subject: [PATCH bpf-next 3/3] ice: xsk: borrow xdp_tx_active logic from i40e

One of the things that commit 5574ff7b7b3d ("i40e: optimize AF_XDP Tx
completion path") introduced was the @xdp_tx_active field. Its usage
from i40e can be adjusted to ice driver and give us positive performance
results.

If the descriptor that @next_dd to points has been sent by HW (its DD
bit is set), then we are sure that there are ICE_TX_THRESH count of
descriptors ready to be cleaned. If @xdp_tx_active is 0 which means that
related xdp_ring is not used for XDP_{TX, REDIRECT} workloads, then we
know how many XSK entries should placed to completion queue, IOW walking
through the ring can be skipped.

Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
---
 drivers/net/ethernet/intel/ice/ice_txrx.h     | 1 +
 drivers/net/ethernet/intel/ice/ice_txrx_lib.c | 1 +
 drivers/net/ethernet/intel/ice/ice_xsk.c      | 7 +++++++
 3 files changed, 9 insertions(+)

diff --git a/drivers/net/ethernet/intel/ice/ice_txrx.h b/drivers/net/ethernet/intel/ice/ice_txrx.h
index f2ebbe2158e7..8dd9c92662ad 100644
--- a/drivers/net/ethernet/intel/ice/ice_txrx.h
+++ b/drivers/net/ethernet/intel/ice/ice_txrx.h
@@ -332,6 +332,7 @@ struct ice_tx_ring {
 	struct ice_ptp_tx *tx_tstamps;
 	spinlock_t tx_lock;
 	u32 txq_teid;			/* Added Tx queue TEID */
+	u16 xdp_tx_active;
 #define ICE_TX_FLAGS_RING_XDP		BIT(0)
 	u8 flags;
 	u8 dcb_tc;			/* Traffic class of ring */
diff --git a/drivers/net/ethernet/intel/ice/ice_txrx_lib.c b/drivers/net/ethernet/intel/ice/ice_txrx_lib.c
index 1dd7e84f41f8..f15c215c973c 100644
--- a/drivers/net/ethernet/intel/ice/ice_txrx_lib.c
+++ b/drivers/net/ethernet/intel/ice/ice_txrx_lib.c
@@ -299,6 +299,7 @@ int ice_xmit_xdp_ring(void *data, u16 size, struct ice_tx_ring *xdp_ring)
 	tx_desc->cmd_type_offset_bsz = ice_build_ctob(ICE_TX_DESC_CMD_EOP, 0,
 						      size, 0);
 
+	xdp_ring->xdp_tx_active++;
 	i++;
 	if (i == xdp_ring->count) {
 		i = 0;
diff --git a/drivers/net/ethernet/intel/ice/ice_xsk.c b/drivers/net/ethernet/intel/ice/ice_xsk.c
index a7f866b3fcd7..8949a7be45c6 100644
--- a/drivers/net/ethernet/intel/ice/ice_xsk.c
+++ b/drivers/net/ethernet/intel/ice/ice_xsk.c
@@ -684,6 +684,7 @@ static void
 ice_clean_xdp_tx_buf(struct ice_tx_ring *xdp_ring, struct ice_tx_buf *tx_buf)
 {
 	xdp_return_frame((struct xdp_frame *)tx_buf->raw_buf);
+	xdp_ring->xdp_tx_active--;
 	dma_unmap_single(xdp_ring->dev, dma_unmap_addr(tx_buf, dma),
 			 dma_unmap_len(tx_buf, len), DMA_TO_DEVICE);
 	dma_unmap_len_set(tx_buf, len, 0);
@@ -713,6 +714,11 @@ bool ice_clean_tx_irq_zc(struct ice_tx_ring *xdp_ring)
 
 again:
 	xsk_frames = 0;
+	if (likely(!xdp_ring->xdp_tx_active)) {
+		xsk_frames = ICE_TX_THRESH;
+		goto skip;
+	}
+
 	ntc = xdp_ring->next_to_clean;
 
 	for (i = 0; i < ICE_TX_THRESH; i++) {
@@ -729,6 +735,7 @@ bool ice_clean_tx_irq_zc(struct ice_tx_ring *xdp_ring)
 		if (ntc >= xdp_ring->count)
 			ntc = 0;
 	}
+skip:
 	xdp_ring->next_to_clean += ICE_TX_THRESH;
 	if (xdp_ring->next_to_clean >= desc_cnt)
 		xdp_ring->next_to_clean -= desc_cnt;
-- 
2.33.1