netdev - [PATCH bpf-next v2 4/4] ice: xsk: borrow xdp_tx

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Date:   Thu, 16 Dec 2021 14:59:58 +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 v2 4/4] 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.

Acked-by: Magnus Karlsson <magnus.karlsson@...el.com>
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      | 8 +++++++-
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/ice/ice_txrx.h b/drivers/net/ethernet/intel/ice/ice_txrx.h
index 9e8b4337d131..5e37d4f57bfa 100644
--- a/drivers/net/ethernet/intel/ice/ice_txrx.h
+++ b/drivers/net/ethernet/intel/ice/ice_txrx.h
@@ -333,6 +333,7 @@ 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 563ea7e7e0b1..a81ade2b7600 100644
--- a/drivers/net/ethernet/intel/ice/ice_xsk.c
+++ b/drivers/net/ethernet/intel/ice/ice_xsk.c
@@ -620,6 +620,7 @@ 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);
@@ -648,6 +649,11 @@ static u16 ice_clean_xdp_irq_zc(struct ice_tx_ring *xdp_ring)
 
 again:
 	cleared_dds++;
+	xsk_frames = 0;
+	if (likely(!xdp_ring->xdp_tx_active)) {
+		xsk_frames = ICE_TX_THRESH;
+		goto skip;
+	}
 
 	ntc = xdp_ring->next_to_clean;
 
@@ -665,7 +671,7 @@ static u16 ice_clean_xdp_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