net/mlx5e: Optimize mlx5e_select_queue

This commit optimizes mlx5e_select_queue for HTB and PTP cases by
short-cutting some checks, without sacrificing performance of the common
non-HTB non-PTP flow.

1. The HTB flow uses the fact that num_tcs == 1 to drop these checks
(it's not possible to attach both mqprio and htb as the root qdisc).
It's also enough to calculate `txq_ix % num_channels` only once, instead
of twice.

2. The PTP flow drops the check for HTB and the second calculation of
`txq_ix % num_channels`.

Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/selq.c b/drivers/net/ethernet/mellanox/mlx5/core/en/selq.c
index b8f1a95..b3ed526 100644 (file)
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/selq.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/selq.c
@@ -164,36 +164,62 @@ u16 mlx5e_select_queue(struct net_device *dev, struct sk_buff *skb,
        if (unlikely(!selq))
                return 0;
 
-       if (unlikely(selq->is_ptp || selq->is_htb)) {
-               if (unlikely(selq->is_htb)) {
-                       txq_ix = mlx5e_select_htb_queue(priv, skb);
-                       if (txq_ix > 0)
-                               return txq_ix;
-               }
+       if (likely(!selq->is_ptp && !selq->is_htb)) {
+               /* No special queues, netdev_pick_tx returns one of the regular ones. */
+
+               txq_ix = netdev_pick_tx(dev, skb, NULL);
+
+               if (selq->num_tcs <= 1)
+                       return txq_ix;
+
+               up = mlx5e_get_up(priv, skb);
+
+               /* Normalize any picked txq_ix to [0, num_channels),
+                * So we can return a txq_ix that matches the channel and
+                * packet UP.
+                */
+               return txq_ix % selq->num_channels + up * selq->num_channels;
+       }
+
+       if (unlikely(selq->is_htb)) {
+               /* num_tcs == 1, shortcut for PTP */
+
+               txq_ix = mlx5e_select_htb_queue(priv, skb);
+               if (txq_ix > 0)
+                       return txq_ix;
 
                if (unlikely(selq->is_ptp && mlx5e_use_ptpsq(skb)))
-                       return mlx5e_select_ptpsq(dev, skb, selq);
+                       return selq->num_channels;
 
                txq_ix = netdev_pick_tx(dev, skb, NULL);
+
                /* Fix netdev_pick_tx() not to choose ptp_channel and HTB txqs.
                 * If they are selected, switch to regular queues.
                 * Driver to select these queues only at mlx5e_select_ptpsq()
                 * and mlx5e_select_htb_queue().
                 */
-               if (unlikely(txq_ix >= selq->num_regular_queues))
-                       txq_ix %= selq->num_regular_queues;
-       } else {
-               txq_ix = netdev_pick_tx(dev, skb, NULL);
+               return txq_ix % selq->num_channels;
        }
 
+       /* PTP is enabled */
+
+       if (mlx5e_use_ptpsq(skb))
+               return mlx5e_select_ptpsq(dev, skb, selq);
+
+       txq_ix = netdev_pick_tx(dev, skb, NULL);
+
+       /* Normalize any picked txq_ix to [0, num_channels). Queues in range
+        * [0, num_regular_queues) will be mapped to the corresponding channel
+        * index, so that we can apply the packet's UP (if num_tcs > 1).
+        * If netdev_pick_tx() picks ptp_channel, switch to a regular queue,
+        * because driver should select the PTP only at mlx5e_select_ptpsq().
+        */
+       txq_ix %= selq->num_channels;
+
        if (selq->num_tcs <= 1)
                return txq_ix;
 
        up = mlx5e_get_up(priv, skb);
 
-       /* Normalize any picked txq_ix to [0, num_channels),
-        * So we can return a txq_ix that matches the channel and
-        * packet UP.
-        */
-       return txq_ix % selq->num_channels + up * selq->num_channels;
+       return txq_ix + up * selq->num_channels;
 }