netdev - [net-next 9/9] net/mlx5e: TX, Improve performance under GSO workload

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Date:   Fri, 31 May 2019 20:09:39 +0000
From:   Saeed Mahameed <saeedm@...lanox.com>
To:     "David S. Miller" <davem@...emloft.net>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Erez Alfasi <ereza@...lanox.com>,
        Tariq Toukan <tariqt@...lanox.com>,
        Saeed Mahameed <saeedm@...lanox.com>
Subject: [net-next 9/9] net/mlx5e: TX, Improve performance under GSO workload

From: Erez Alfasi <ereza@...lanox.com>

__netdev_tx_sent_queue() was introduced by:
commit 3e59020abf0f ("net: bql: add __netdev_tx_sent_queue()")

BQL counters should be updated without flipping/caring about
BQL status, if the current skb has xmit_more set.

Using __netdev_tx_sent_queue() avoids messing with BQL stop
flag, increases performance on GSO workload by keeping
doorbells to the minimum required and also sparing atomic
operations.

Signed-off-by: Erez Alfasi <ereza@...lanox.com>
Reviewed-by: Tariq Toukan <tariqt@...lanox.com>
Signed-off-by: Saeed Mahameed <saeedm@...lanox.com>
---
 drivers/net/ethernet/mellanox/mlx5/core/en_tx.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c
index 195a7d903cec..6fd6d5356246 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c
@@ -301,6 +301,7 @@ mlx5e_txwqe_complete(struct mlx5e_txqsq *sq, struct sk_buff *skb,
 		     bool xmit_more)
 {
 	struct mlx5_wq_cyc *wq = &sq->wq;
+	bool send_doorbell;
 
 	wi->num_bytes = num_bytes;
 	wi->num_dma = num_dma;
@@ -310,8 +311,6 @@ mlx5e_txwqe_complete(struct mlx5e_txqsq *sq, struct sk_buff *skb,
 	cseg->opmod_idx_opcode = cpu_to_be32((sq->pc << 8) | opcode);
 	cseg->qpn_ds           = cpu_to_be32((sq->sqn << 8) | ds_cnt);
 
-	netdev_tx_sent_queue(sq->txq, num_bytes);
-
 	if (unlikely(skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP))
 		skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;
 
@@ -321,7 +320,9 @@ mlx5e_txwqe_complete(struct mlx5e_txqsq *sq, struct sk_buff *skb,
 		sq->stats->stopped++;
 	}
 
-	if (!xmit_more || netif_xmit_stopped(sq->txq))
+	send_doorbell = __netdev_tx_sent_queue(sq->txq, num_bytes,
+					       xmit_more);
+	if (send_doorbell)
 		mlx5e_notify_hw(wq, sq->pc, sq->uar_map, cseg);
 }
 
-- 
2.21.0