net/mlx5e: Optimize poll ICOSQ completion queue

UMR operations are more frequent and important.
Check them first, and add a compiler branch predictor hint.

According to current design, ICOSQ CQ can contain at most one
pending CQE per napi. Poll function is optimized accordingly.

Performance:
Single-stream packet-rate tested with pktgen.
Packets are dropped in tc level to zoom into driver data-path.
Larger gain is expected for larger packet sizes, as BW is higher
and UMR posts are more frequent.

---------------------------------------------
packet size | before    | after     | gain  |
64B         | 4,092,370 | 4,113,306 |  0.5% |
1024B       | 3,421,435 | 3,633,819 |  6.2% |

Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Cc: kernel-team@fb.com
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_txrx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_txrx.c
index 43729ec..491e83d 100644 (file)
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_txrx.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_txrx.c
@@ -49,10 +49,40 @@ struct mlx5_cqe64 *mlx5e_get_cqe(struct mlx5e_cq *cq)
        return cqe;
 }
 
+static inline void mlx5e_poll_ico_single_cqe(struct mlx5e_cq *cq,
+                                            struct mlx5e_icosq *sq,
+                                            struct mlx5_cqe64 *cqe,
+                                            u16 *sqcc)
+{
+       struct mlx5_wq_cyc *wq = &sq->wq;
+       u16 ci = be16_to_cpu(cqe->wqe_counter) & wq->sz_m1;
+       struct mlx5e_sq_wqe_info *icowi = &sq->db.ico_wqe[ci];
+       struct mlx5e_rq *rq = &sq->channel->rq;
+
+       prefetch(rq);
+       mlx5_cqwq_pop(&cq->wq);
+       *sqcc += icowi->num_wqebbs;
+
+       if (unlikely((cqe->op_own >> 4) != MLX5_CQE_REQ)) {
+               WARN_ONCE(true, "mlx5e: Bad OP in ICOSQ CQE: 0x%x\n",
+                         cqe->op_own);
+               return;
+       }
+
+       if (likely(icowi->opcode == MLX5_OPCODE_UMR)) {
+               mlx5e_post_rx_mpwqe(rq);
+               return;
+       }
+
+       if (unlikely(icowi->opcode != MLX5_OPCODE_NOP))
+               WARN_ONCE(true,
+                         "mlx5e: Bad OPCODE in ICOSQ WQE info: 0x%x\n",
+                         icowi->opcode);
+}
+
 static void mlx5e_poll_ico_cq(struct mlx5e_cq *cq)
 {
        struct mlx5e_icosq *sq = container_of(cq, struct mlx5e_icosq, cq);
-       struct mlx5_wq_cyc *wq;
        struct mlx5_cqe64 *cqe;
        u16 sqcc;
 
@@ -63,39 +93,13 @@ static void mlx5e_poll_ico_cq(struct mlx5e_cq *cq)
        if (likely(!cqe))
                return;
 
-       wq = &sq->wq;
-
        /* sq->cc must be updated only after mlx5_cqwq_update_db_record(),
         * otherwise a cq overrun may occur
         */
        sqcc = sq->cc;
 
-       do {
-               u16 ci = be16_to_cpu(cqe->wqe_counter) & wq->sz_m1;
-               struct mlx5e_sq_wqe_info *icowi = &sq->db.ico_wqe[ci];
-
-               mlx5_cqwq_pop(&cq->wq);
-               sqcc += icowi->num_wqebbs;
-
-               if (unlikely((cqe->op_own >> 4) != MLX5_CQE_REQ)) {
-                       WARN_ONCE(true, "mlx5e: Bad OP in ICOSQ CQE: 0x%x\n",
-                                 cqe->op_own);
-                       break;
-               }
-
-               switch (icowi->opcode) {
-               case MLX5_OPCODE_NOP:
-                       break;
-               case MLX5_OPCODE_UMR:
-                       mlx5e_post_rx_mpwqe(&sq->channel->rq);
-                       break;
-               default:
-                       WARN_ONCE(true,
-                                 "mlx5e: Bad OPCODE in ICOSQ WQE info: 0x%x\n",
-                                 icowi->opcode);
-               }
-
-       } while ((cqe = mlx5e_get_cqe(cq)));
+       /* by design, there's only a single cqe */
+       mlx5e_poll_ico_single_cqe(cq, sq, cqe, &sqcc);
 
        mlx5_cqwq_update_db_record(&cq->wq);