mlx5en: Remove the DRBR and associated logic in the transmit path.

The hardware queues are deep enough currently and using the DRBR and associated
callbacks only leads to more task switching in the TX path. The is also a race
setting the queue_state which can lead to hung TX rings.

Submitted by:   hselasky@
Approved by:    hselasky (mentor)
MFC after:      1 week
Sponsored by:   Mellanox Technologies

1 files changed, 5 insertions, 93 deletions

diff --git a/sys/dev/mlx5/mlx5_en/mlx5_en_tx.c b/sys/dev/mlx5/mlx5_en/mlx5_en_tx.c
index 40d8157c6771..e7ee7f41c574 100644
--- a/sys/dev/mlx5/mlx5_en/mlx5_en_tx.c
+++ b/sys/dev/mlx5/mlx5_en/mlx5_en_tx.c
@@ -249,10 +249,6 @@ mlx5e_get_header_size(struct mbuf *mb)
 	return (eth_hdr_len);
 }
 
-/*
- * The return value is not going back to the stack because of
- * the drbr
- */
 static int
 mlx5e_sq_xmit(struct mlx5e_sq *sq, struct mbuf **mbp)
 {
@@ -269,13 +265,9 @@ mlx5e_sq_xmit(struct mlx5e_sq *sq, struct mbuf **mbp)
 	u16 pi;
 	u8 opcode;
 
-	/*
-	 * Return ENOBUFS if the queue is full, this may trigger reinsertion
-	 * of the mbuf into the drbr (see mlx5e_xmit_locked)
-	 */
-	if (unlikely(!mlx5e_sq_has_room_for(sq, 2 * MLX5_SEND_WQE_MAX_WQEBBS))) {
+	/* Return ENOBUFS if the queue is full */
+	if (unlikely(!mlx5e_sq_has_room_for(sq, 2 * MLX5_SEND_WQE_MAX_WQEBBS)))
 		return (ENOBUFS);
-	}
 
 	/* Align SQ edge with NOPs to avoid WQE wrap around */
 	pi = ((~sq->pc) & sq->wq.sz_m1);
@@ -497,68 +489,11 @@ mlx5e_poll_tx_cq(struct mlx5e_sq *sq, int budget)
 	atomic_thread_fence_rel();
 
 	sq->cc = sqcc;
-
-	if (sq->sq_tq != NULL &&
-	    atomic_cmpset_int(&sq->queue_state, MLX5E_SQ_FULL, MLX5E_SQ_READY))
-		taskqueue_enqueue(sq->sq_tq, &sq->sq_task);
 }
 
 static int
 mlx5e_xmit_locked(struct ifnet *ifp, struct mlx5e_sq *sq, struct mbuf *mb)
 {
-	struct mbuf *next;
-	int err = 0;
-
-	if (likely(mb != NULL)) {
-		/*
-		 * If we can't insert mbuf into drbr, try to xmit anyway.
-		 * We keep the error we got so we could return that after xmit.
-		 */
-		err = drbr_enqueue(ifp, sq->br, mb);
-	}
-
-	/*
-	 * Check if the network interface is closed or if the SQ is
-	 * being stopped:
-	 */
-	if (unlikely((ifp->if_drv_flags & IFF_DRV_RUNNING) == 0 ||
-	    sq->stopped != 0))
-		return (err);
-
-	/* Process the queue */
-	while ((next = drbr_peek(ifp, sq->br)) != NULL) {
-		if (mlx5e_sq_xmit(sq, &next) != 0) {
-			if (next != NULL) {
-				drbr_putback(ifp, sq->br, next);
-				atomic_store_rel_int(&sq->queue_state, MLX5E_SQ_FULL);
-				break;
-			}
-		}
-		drbr_advance(ifp, sq->br);
-	}
-	/* Check if we need to write the doorbell */
-	if (likely(sq->doorbell.d64 != 0)) {
-		mlx5e_tx_notify_hw(sq, sq->doorbell.d32, 0);
-		sq->doorbell.d64 = 0;
-	}
-	/*
-	 * Check if we need to start the event timer which flushes the
-	 * transmit ring on timeout:
-	 */
-	if (unlikely(sq->cev_next_state == MLX5E_CEV_STATE_INITIAL &&
-	    sq->cev_factor != 1)) {
-		/* start the timer */
-		mlx5e_sq_cev_timeout(sq);
-	} else {
-		/* don't send NOPs yet */
-		sq->cev_next_state = MLX5E_CEV_STATE_HOLD_NOPS;
-	}
-	return (err);
-}
-
-static int
-mlx5e_xmit_locked_no_br(struct ifnet *ifp, struct mlx5e_sq *sq, struct mbuf *mb)
-{
 	int err = 0;
 
 	if (unlikely((ifp->if_drv_flags & IFF_DRV_RUNNING) == 0 ||
@@ -624,18 +559,9 @@ mlx5e_xmit(struct ifnet *ifp, struct mbuf *mb)
 		return (ENXIO);
 	}
 
-	if (unlikely(sq->br == NULL)) {
-		/* rate limited traffic */
-		mtx_lock(&sq->lock);
-		ret = mlx5e_xmit_locked_no_br(ifp, sq, mb);
-		mtx_unlock(&sq->lock);
-	} else if (mtx_trylock(&sq->lock)) {
-		ret = mlx5e_xmit_locked(ifp, sq, mb);
-		mtx_unlock(&sq->lock);
-	} else {
-		ret = drbr_enqueue(ifp, sq->br, mb);
-		taskqueue_enqueue(sq->sq_tq, &sq->sq_task);
-	}
+	mtx_lock(&sq->lock);
+	ret = mlx5e_xmit_locked(ifp, sq, mb);
+	mtx_unlock(&sq->lock);
 
 	return (ret);
 }
@@ -650,17 +576,3 @@ mlx5e_tx_cq_comp(struct mlx5_core_cq *mcq)
 	mlx5e_cq_arm(&sq->cq, MLX5_GET_DOORBELL_LOCK(&sq->priv->doorbell_lock));
 	mtx_unlock(&sq->comp_lock);
 }
-
-void
-mlx5e_tx_que(void *context, int pending)
-{
-	struct mlx5e_sq *sq = context;
-	struct ifnet *ifp = sq->ifp;
-
-	if (ifp->if_drv_flags & IFF_DRV_RUNNING) {
-		mtx_lock(&sq->lock);
-		if (!drbr_empty(ifp, sq->br))
-			mlx5e_xmit_locked(ifp, sq, NULL);
-		mtx_unlock(&sq->lock);
-	}
-}