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Commit cc26a490 authored by Tariq Toukan's avatar Tariq Toukan Committed by David S. Miller
Browse files

net/mlx4_en: Improve transmit CQ polling 



Several small performance improvements in TX CQ polling,
including:
- Compiler branch predictor hints.
- Minimize variables scope.
- More proper check of cq type.
- Use boolean instead of int for a binary indication.

Performance tests:
Tested on ConnectX3Pro, Intel(R) Xeon(R) CPU E5-2680 v3 @ 2.50GHz

Packet-rate tests for both regular stack and XDP use cases:
No noticeable gain, no degradation.

Signed-off-by: default avatarTariq Toukan <tariqt@mellanox.com>
Reviewed-by: default avatarSaeed Mahameed <saeedm@mellanox.com>
Cc: kernel-team@fb.com
Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 9bcee89a

drivers/net/ethernet/mellanox/mlx4/en_tx.c

+7 −6
Original line number Original line Diff line number Diff line
@@ -402,8 +402,7 @@ static bool mlx4_en_process_tx_cq(struct net_device *dev, 
	struct mlx4_cq *mcq = &cq->mcq;

	struct mlx4_cq *mcq = &cq->mcq;

	struct mlx4_en_tx_ring *ring = priv->tx_ring[cq->type][cq->ring];

	struct mlx4_en_tx_ring *ring = priv->tx_ring[cq->type][cq->ring];

	struct mlx4_cqe *cqe;

	struct mlx4_cqe *cqe;

	u16 index;

	u16 index, ring_index, stamp_index;

	u16 new_index, ring_index, stamp_index;

	u32 txbbs_skipped = 0;

	u32 txbbs_skipped = 0;

	u32 txbbs_stamp = 0;

	u32 txbbs_stamp = 0;

	u32 cons_index = mcq->cons_index;

	u32 cons_index = mcq->cons_index;
@@ -418,7 +417,7 @@ static bool mlx4_en_process_tx_cq(struct net_device *dev, 
	u32 last_nr_txbb;

	u32 last_nr_txbb;

	u32 ring_cons;

	u32 ring_cons;





	if (!priv->port_up)

	if (unlikely(!priv->port_up))

		return true;

		return true;





	netdev_txq_bql_complete_prefetchw(ring->tx_queue);

	netdev_txq_bql_complete_prefetchw(ring->tx_queue);
@@ -433,6 +432,8 @@ static bool mlx4_en_process_tx_cq(struct net_device *dev, 
	/* Process all completed CQEs */

	/* Process all completed CQEs */

	while (XNOR(cqe->owner_sr_opcode & MLX4_CQE_OWNER_MASK,

	while (XNOR(cqe->owner_sr_opcode & MLX4_CQE_OWNER_MASK,

			cons_index & size) && (done < budget)) {

			cons_index & size) && (done < budget)) {

		u16 new_index;



		/*

		/*

		 * make sure we read the CQE after we read the

		 * make sure we read the CQE after we read the

		 * ownership bit

		 * ownership bit
@@ -479,7 +480,6 @@ static bool mlx4_en_process_tx_cq(struct net_device *dev, 
		cqe = mlx4_en_get_cqe(buf, index, priv->cqe_size) + factor;

		cqe = mlx4_en_get_cqe(buf, index, priv->cqe_size) + factor;

	}

	}







	/*

	/*

	 * To prevent CQ overflow we first update CQ consumer and only then

	 * To prevent CQ overflow we first update CQ consumer and only then

	 * the ring consumer.

	 * the ring consumer.
@@ -492,7 +492,7 @@ static bool mlx4_en_process_tx_cq(struct net_device *dev, 
	ACCESS_ONCE(ring->last_nr_txbb) = last_nr_txbb;

	ACCESS_ONCE(ring->last_nr_txbb) = last_nr_txbb;

	ACCESS_ONCE(ring->cons) = ring_cons + txbbs_skipped;

	ACCESS_ONCE(ring->cons) = ring_cons + txbbs_skipped;





	if (ring->free_tx_desc == mlx4_en_recycle_tx_desc)

	if (cq->type == TX_XDP)

		return done < budget;

		return done < budget;





	netdev_tx_completed_queue(ring->tx_queue, packets, bytes);

	netdev_tx_completed_queue(ring->tx_queue, packets, bytes);
@@ -504,6 +504,7 @@ static bool mlx4_en_process_tx_cq(struct net_device *dev, 
		netif_tx_wake_queue(ring->tx_queue);

		netif_tx_wake_queue(ring->tx_queue);

		ring->wake_queue++;

		ring->wake_queue++;

	}

	}



	return done < budget;

	return done < budget;

}

}
@@ -524,7 +525,7 @@ int mlx4_en_poll_tx_cq(struct napi_struct *napi, int budget) 
	struct mlx4_en_cq *cq = container_of(napi, struct mlx4_en_cq, napi);

	struct mlx4_en_cq *cq = container_of(napi, struct mlx4_en_cq, napi);

	struct net_device *dev = cq->dev;

	struct net_device *dev = cq->dev;

	struct mlx4_en_priv *priv = netdev_priv(dev);

	struct mlx4_en_priv *priv = netdev_priv(dev);

	int clean_complete;

	bool clean_complete;





	clean_complete = mlx4_en_process_tx_cq(dev, cq, budget);

	clean_complete = mlx4_en_process_tx_cq(dev, cq, budget);

	if (!clean_complete)

	if (!clean_complete)