[Bug 1200] mlx5_tx_handle_completion: bad timestamp

[bugzilla@dpdk.org]

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https://bugs.dpdk.org/show_bug.cgi?id=1200

            Bug ID: 1200
           Summary: mlx5_tx_handle_completion: bad timestamp
           Product: DPDK
           Version: 22.03
          Hardware: x86
                OS: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: core
          Assignee: dev@dpdk.org
          Reporter: 7532yahoo@gmail.com
  Target Milestone: ---

In the file `dpdk/drivers/net/mlx5/mlx5_tx.c` method
`mlx5_tx_handle_completion` I inspect the timestamp field of a cqe:

@@ -192,6 +196,9 @@ mlx5_tx_handle_completion(struct mlx5_txq_data
*__rte_restrict txq,

                cqe = &txq->cqes[txq->cq_ci & txq->cqe_m];
                ret = check_cqe(cqe, txq->cqe_s, txq->cq_ci);
+    if (ret==MLX5_CQE_STATUS_HW_OWN) {
+      printf("line:%d cqe timestamp: %lu\n", __LINE__, cqe->timestamp);
+    }

Consider transmitting several thousand packets. This print to stdout with
regard to the timestamp,

* prints 0 for timestamp for the first ~2000 packet completions
* prints non-zero numbers thereafter, however, not monotonically increasing
e.g. completion event timestamp for occurrence  N is 10x smaller than N-1

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