From: Tariq Toukan <tariqt@mellanox.com>
To: Jesper Dangaard Brouer <brouer@redhat.com>,
        Achiad Shochat <achiad@mellanox.com>,
        Rana Shahout <ranas@mellanox.com>,
        Saeed Mahameed <saeedm@mellanox.com>
Subject: [PATCH] net/mlx5e: force tx skb bulking
Date: Wed, 17 Aug 2016 12:14:51 +0300
Message-Id: <1471425291-1782-1-git-send-email-tariqt@mellanox.com>

From: Achiad Shochat <achiad@mellanox.com>

To improve SW message rate in case HW is faster.
Heuristically detect cases where the message rate is high and there
is still no skb bulking and if so, stops the txq for a while trying
to force the bulking.

Change-Id: Icb925135e69b030943cb4666117c47d1cc04da97
---
 drivers/net/ethernet/mellanox/mlx5/core/en.h    | 5 +++++
 drivers/net/ethernet/mellanox/mlx5/core/en_tx.c | 9 ++++++++-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en.h b/drivers/net/ethernet/mellanox/mlx5/core/en.h
index 74edd01..78a0661 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en.h
@@ -394,6 +394,10 @@ enum {
 	MLX5E_SQ_STATE_TX_TIMEOUT,
 };
 
+enum {
+	MLX5E_SQ_STOP_ONCE,
+};
+
 struct mlx5e_ico_wqe_info {
 	u8  opcode;
 	u8  num_wqebbs;
@@ -403,6 +407,7 @@ struct mlx5e_sq {
 	/* data path */
 
 	/* dirtied @completion */
+	unsigned long              flags;
 	u16                        cc;
 	u32                        dma_fifo_cc;
 
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c
index e073bf59..034eef0 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c
@@ -351,8 +351,10 @@ static netdev_tx_t mlx5e_sq_xmit(struct mlx5e_sq *sq, struct sk_buff *skb)
 	if (unlikely(skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP))
 		skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;
 
-	if (unlikely(!mlx5e_sq_has_room_for(sq, MLX5E_SQ_STOP_ROOM))) {
+	if (test_bit(MLX5E_SQ_STOP_ONCE, &sq->flags) ||
+	    unlikely(!mlx5e_sq_has_room_for(sq, MLX5E_SQ_STOP_ROOM))) {
 		netif_tx_stop_queue(sq->txq);
+		clear_bit(MLX5E_SQ_STOP_ONCE, &sq->flags);
 		sq->stats.stopped++;
 	}
 
@@ -429,6 +431,7 @@ bool mlx5e_poll_tx_cq(struct mlx5e_cq *cq, int napi_budget)
 	u32 dma_fifo_cc;
 	u32 nbytes;
 	u16 npkts;
+	u16 ncqes;
 	u16 sqcc;
 	int i;
 
@@ -439,6 +442,7 @@ bool mlx5e_poll_tx_cq(struct mlx5e_cq *cq, int napi_budget)
 
 	npkts = 0;
 	nbytes = 0;
+	ncqes = 0;
 
 	/* sq->cc must be updated only after mlx5_cqwq_update_db_record(),
 	 * otherwise a cq overrun may occur
@@ -458,6 +462,7 @@ bool mlx5e_poll_tx_cq(struct mlx5e_cq *cq, int napi_budget)
 			break;
 
 		mlx5_cqwq_pop(&cq->wq);
+		ncqes++;
 
 		wqe_counter = be16_to_cpu(cqe->wqe_counter);
 
@@ -508,6 +513,8 @@ bool mlx5e_poll_tx_cq(struct mlx5e_cq *cq, int napi_budget)
 
 	sq->dma_fifo_cc = dma_fifo_cc;
 	sq->cc = sqcc;
+	if ((npkts > 7) && ((npkts >> (ilog2(ncqes))) < 8))
+		set_bit(MLX5E_SQ_STOP_ONCE, &sq->flags);
 
 	netdev_tx_completed_queue(sq->txq, npkts, nbytes);
 
-- 
1.8.3.1