net/mlx5e: TX, Use actual WQE size for SQ edge fill

We fill SQ edge with NOPs to avoid WQEs wrap.
Here, instead of doing that in advance for the maximum possible
WQE size, we do it on-demand using the actual WQE size.
We re-order some parts in mlx5e_sq_xmit to finish the calculation
of WQE size (ds_cnt) before doing any writes to the WQE buffer.

When SQ work queue is fragmented (introduced in an downstream patch),
dealing with WQE wraps becomes more frequent. This change would drastically
reduce the overhead in this case.

Performance tests:
ConnectX-5 100Gbps, CPU: Intel(R) Xeon(R) CPU E5-2680 v3 @ 2.50GHz
Packet rate of 64B packets, single transmit ring, size 8K.

Before: 14.9 Mpps
After:  15.8 Mpps

Improvement of 6%.

Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/ipoib/ipoib.h b/drivers/net/ethernet/mellanox/mlx5/core/ipoib/ipoib.h
index 6d9053bcbe95..45a11864e544 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/ipoib/ipoib.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/ipoib/ipoib.h
@@ -93,6 +93,29 @@ const struct mlx5e_profile *mlx5i_pkey_get_profile(void);
 /* Extract mlx5e_priv from IPoIB netdev */
 #define mlx5i_epriv(netdev) ((void *)(((struct mlx5i_priv *)netdev_priv(netdev))->mlx5e_priv))
 
+struct mlx5_wqe_eth_pad {
+	u8 rsvd0[16];
+};
+
+struct mlx5i_tx_wqe {
+	struct mlx5_wqe_ctrl_seg     ctrl;
+	struct mlx5_wqe_datagram_seg datagram;
+	struct mlx5_wqe_eth_pad      pad;
+	struct mlx5_wqe_eth_seg      eth;
+	struct mlx5_wqe_data_seg     data[0];
+};
+
+static inline void mlx5i_sq_fetch_wqe(struct mlx5e_txqsq *sq,
+				      struct mlx5i_tx_wqe **wqe,
+				      u16 *pi)
+{
+	struct mlx5_wq_cyc *wq = &sq->wq;
+
+	*pi  = mlx5_wq_cyc_ctr2ix(wq, sq->pc);
+	*wqe = mlx5_wq_cyc_get_wqe(wq, *pi);
+	memset(*wqe, 0, sizeof(**wqe));
+}
+
 netdev_tx_t mlx5i_sq_xmit(struct mlx5e_txqsq *sq, struct sk_buff *skb,
 			  struct mlx5_av *av, u32 dqpn, u32 dqkey);
 void mlx5i_handle_rx_cqe(struct mlx5e_rq *rq, struct mlx5_cqe64 *cqe);