MFC r312536:

Allow transmit packet bufring in software to be disabled.

- Add new sysctl node to control the transmit packet bufring.

- Add optimised version of the transmit routine which output packets
directly to the DMA ring instead of using bufring in case the transmit
lock is congested. This can reduce the number of taskswitches which in
turn influence the overall system CPU usage, depending on the
workload.

- Add " TX" suffix to debug name for transmit mutexes to silence some
witness warnings about aquiring duplicate locks having same name.

Sponsored by:		Mellanox Technologies
Suggested by:		gallatin @

1 files changed, 38 insertions, 30 deletions

diff --git a/sys/dev/mlx5/mlx5_en/mlx5_en_main.c b/sys/dev/mlx5/mlx5_en/mlx5_en_main.c
index 5ba2f02..0435179 100644
--- a/sys/dev/mlx5/mlx5_en/mlx5_en_main.c
+++ b/sys/dev/mlx5/mlx5_en/mlx5_en_main.c
@@ -439,7 +439,8 @@ mlx5e_update_stats_work(struct work_struct *work)
 			tso_packets += sq_stats->tso_packets;
 			tso_bytes += sq_stats->tso_bytes;
 			tx_queue_dropped += sq_stats->dropped;
-			tx_queue_dropped += sq_br->br_drops;
+			if (sq_br != NULL)
+				tx_queue_dropped += sq_br->br_drops;
 			tx_defragged += sq_stats->defragged;
 			tx_offload_none += sq_stats->csum_offload_none;
 		}
@@ -1001,34 +1002,37 @@ mlx5e_create_sq(struct mlx5e_channel *c,
 	sq->priv = priv;
 	sq->tc = tc;
 
-	sq->br = buf_ring_alloc(MLX5E_SQ_TX_QUEUE_SIZE, M_MLX5EN,
-	    M_WAITOK, &sq->lock);
-	if (sq->br == NULL) {
-		if_printf(c->ifp, "%s: Failed allocating sq drbr buffer\n",
-		    __func__);
-		err = -ENOMEM;
-		goto err_free_sq_db;
-	}
+	/* check if we should allocate a second packet buffer */
+	if (priv->params_ethtool.tx_bufring_disable == 0) {
+		sq->br = buf_ring_alloc(MLX5E_SQ_TX_QUEUE_SIZE, M_MLX5EN,
+		    M_WAITOK, &sq->lock);
+		if (sq->br == NULL) {
+			if_printf(c->ifp, "%s: Failed allocating sq drbr buffer\n",
+			    __func__);
+			err = -ENOMEM;
+			goto err_free_sq_db;
+		}
 
-	sq->sq_tq = taskqueue_create_fast("mlx5e_que", M_WAITOK,
-	    taskqueue_thread_enqueue, &sq->sq_tq);
-	if (sq->sq_tq == NULL) {
-		if_printf(c->ifp, "%s: Failed allocating taskqueue\n",
-		    __func__);
-		err = -ENOMEM;
-		goto err_free_drbr;
-	}
+		sq->sq_tq = taskqueue_create_fast("mlx5e_que", M_WAITOK,
+		    taskqueue_thread_enqueue, &sq->sq_tq);
+		if (sq->sq_tq == NULL) {
+			if_printf(c->ifp, "%s: Failed allocating taskqueue\n",
+			    __func__);
+			err = -ENOMEM;
+			goto err_free_drbr;
+		}
 
-	TASK_INIT(&sq->sq_task, 0, mlx5e_tx_que, sq);
+		TASK_INIT(&sq->sq_task, 0, mlx5e_tx_que, sq);
 #ifdef RSS
-	cpu_id = rss_getcpu(c->ix % rss_getnumbuckets());
-	CPU_SETOF(cpu_id, &cpu_mask);
-	taskqueue_start_threads_cpuset(&sq->sq_tq, 1, PI_NET, &cpu_mask,
-	    "%s TX SQ%d.%d CPU%d", c->ifp->if_xname, c->ix, tc, cpu_id);
+		cpu_id = rss_getcpu(c->ix % rss_getnumbuckets());
+		CPU_SETOF(cpu_id, &cpu_mask);
+		taskqueue_start_threads_cpuset(&sq->sq_tq, 1, PI_NET, &cpu_mask,
+		    "%s TX SQ%d.%d CPU%d", c->ifp->if_xname, c->ix, tc, cpu_id);
 #else
-	taskqueue_start_threads(&sq->sq_tq, 1, PI_NET,
-	    "%s TX SQ%d.%d", c->ifp->if_xname, c->ix, tc);
+		taskqueue_start_threads(&sq->sq_tq, 1, PI_NET,
+		    "%s TX SQ%d.%d", c->ifp->if_xname, c->ix, tc);
 #endif
+	}
 	snprintf(buffer, sizeof(buffer), "txstat%dtc%d", c->ix, tc);
 	mlx5e_create_stats(&sq->stats.ctx, SYSCTL_CHILDREN(priv->sysctl_ifnet),
 	    buffer, mlx5e_sq_stats_desc, MLX5E_SQ_STATS_NUM,
@@ -1061,9 +1065,12 @@ mlx5e_destroy_sq(struct mlx5e_sq *sq)
 	mlx5e_free_sq_db(sq);
 	mlx5_wq_destroy(&sq->wq_ctrl);
 	mlx5_unmap_free_uar(sq->priv->mdev, &sq->uar);
-	taskqueue_drain(sq->sq_tq, &sq->sq_task);
-	taskqueue_free(sq->sq_tq);
-	buf_ring_free(sq->br, M_MLX5EN);
+	if (sq->sq_tq != NULL) {
+		taskqueue_drain(sq->sq_tq, &sq->sq_task);
+		taskqueue_free(sq->sq_tq);
+	}
+	if (sq->br != NULL)
+		buf_ring_free(sq->br, M_MLX5EN);
 }
 
 int
@@ -1511,9 +1518,10 @@ mlx5e_chan_mtx_init(struct mlx5e_channel *c)
 	for (tc = 0; tc < c->num_tc; tc++) {
 		struct mlx5e_sq *sq = c->sq + tc;
 
-		mtx_init(&sq->lock, "mlx5tx", MTX_NETWORK_LOCK, MTX_DEF);
-		mtx_init(&sq->comp_lock, "mlx5comp", MTX_NETWORK_LOCK,
-		    MTX_DEF);
+		mtx_init(&sq->lock, "mlx5tx",
+		    MTX_NETWORK_LOCK " TX", MTX_DEF);
+		mtx_init(&sq->comp_lock, "mlx5comp",
+		    MTX_NETWORK_LOCK " TX", MTX_DEF);
 
 		callout_init_mtx(&sq->cev_callout, &sq->lock, 0);