[PATCH v3 2/3] net/mlx5: fix Tx stats error counter

[Shahaf Shuler <shahafs@mellanox.com>]

The current Tx error counter counts, according to its description,
the total number of packets not sent when TX ring full. It is reported to
application as part of oerrors field.

Putting aside the fact there is no logic which increment this counter,
the behaviour of the PMD is wrong.
The drop due to full ring is not the statistic that should be set on
oerrors field. Such number can be counted by the application using the
return value of the Tx burst function.
The number that should be set there is the number of packets the device
could not transmit in any way, even when it has resources.

Therefore, replace this counter to count the total number of failed
transmitted packets.
In addition, add the logic to increment it on the different cases.

Fixes: 87011737b715 ("mlx5: add software counters")
Cc: stable@dpdk.org
Cc: adrien.mazarguil@6wind.com

Signed-off-by: Shahaf Shuler <shahafs@mellanox.com>
---
on v3:
 - This patch is new on v3 to address the comment provided on v2.
---
 drivers/net/mlx5/mlx5_rxtx.c  | 20 +++++++++++++++-----
 drivers/net/mlx5/mlx5_rxtx.h  |  2 +-
 drivers/net/mlx5/mlx5_stats.c |  4 ++--
 3 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/drivers/net/mlx5/mlx5_rxtx.c b/drivers/net/mlx5/mlx5_rxtx.c
index fe9e7eac0..7567f2329 100644
--- a/drivers/net/mlx5/mlx5_rxtx.c
+++ b/drivers/net/mlx5/mlx5_rxtx.c
@@ -406,8 +406,10 @@ mlx5_tx_burst(void *dpdk_txq, struct rte_mbuf **pkts, uint16_t pkts_n)
 #ifdef MLX5_PMD_SOFT_COUNTERS
 		total_length = length;
 #endif
-		if (length < (MLX5_WQE_DWORD_SIZE + 2))
+		if (length < (MLX5_WQE_DWORD_SIZE + 2)) {
+			txq->stats.oerrors++;
 			break;
+		}
 		/* Update element. */
 		(*txq->elts)[elts_head & elts_m] = buf;
 		/* Prefetch next buffer data. */
@@ -481,8 +483,10 @@ mlx5_tx_burst(void *dpdk_txq, struct rte_mbuf **pkts, uint16_t pkts_n)
 					cs_flags |= MLX5_ETH_WQE_L4_CSUM;
 				}
 				if (unlikely(tso_header_sz >
-					     MLX5_MAX_TSO_HEADER))
+					     MLX5_MAX_TSO_HEADER)) {
+					txq->stats.oerrors++;
 					break;
+				}
 				copy_b = tso_header_sz - pkt_inline_sz;
 				/* First seg must contain all headers. */
 				assert(copy_b <= length);
@@ -843,8 +847,10 @@ mlx5_tx_burst_mpw(void *dpdk_txq, struct rte_mbuf **pkts, uint16_t pkts_n)
 		if (max_elts < segs_n)
 			break;
 		/* Do not bother with large packets MPW cannot handle. */
-		if (segs_n > MLX5_MPW_DSEG_MAX)
+		if (segs_n > MLX5_MPW_DSEG_MAX) {
+			txq->stats.oerrors++;
 			break;
+		}
 		max_elts -= segs_n;
 		--pkts_n;
 		/* Should we enable HW CKSUM offload */
@@ -1064,8 +1070,10 @@ mlx5_tx_burst_mpw_inline(void *dpdk_txq, struct rte_mbuf **pkts,
 		if (max_elts < segs_n)
 			break;
 		/* Do not bother with large packets MPW cannot handle. */
-		if (segs_n > MLX5_MPW_DSEG_MAX)
+		if (segs_n > MLX5_MPW_DSEG_MAX) {
+			txq->stats.oerrors++;
 			break;
+		}
 		max_elts -= segs_n;
 		--pkts_n;
 		/*
@@ -1353,8 +1361,10 @@ mlx5_tx_burst_empw(void *dpdk_txq, struct rte_mbuf **pkts, uint16_t pkts_n)
 		if (max_elts - j < segs_n)
 			break;
 		/* Do not bother with large packets MPW cannot handle. */
-		if (segs_n > MLX5_MPW_DSEG_MAX)
+		if (segs_n > MLX5_MPW_DSEG_MAX) {
+			txq->stats.oerrors++;
 			break;
+		}
 		/* Should we enable HW CKSUM offload. */
 		if (buf->ol_flags &
 		    (PKT_TX_IP_CKSUM | PKT_TX_TCP_CKSUM | PKT_TX_UDP_CKSUM))
diff --git a/drivers/net/mlx5/mlx5_rxtx.h b/drivers/net/mlx5/mlx5_rxtx.h
index 033e70f25..107ada0f5 100644
--- a/drivers/net/mlx5/mlx5_rxtx.h
+++ b/drivers/net/mlx5/mlx5_rxtx.h
@@ -75,7 +75,7 @@ struct mlx5_txq_stats {
 	uint64_t opackets; /**< Total of successfully sent packets. */
 	uint64_t obytes; /**< Total of successfully sent bytes. */
 #endif
-	uint64_t odropped; /**< Total of packets not sent when TX ring full. */
+	uint64_t oerrors; /**< Total number of failed transmitted packets. */
 };
 
 /* Flow director queue structure. */
diff --git a/drivers/net/mlx5/mlx5_stats.c b/drivers/net/mlx5/mlx5_stats.c
index d443e1336..06348c8a1 100644
--- a/drivers/net/mlx5/mlx5_stats.c
+++ b/drivers/net/mlx5/mlx5_stats.c
@@ -360,13 +360,13 @@ mlx5_stats_get(struct rte_eth_dev *dev, struct rte_eth_stats *stats)
 			tmp.q_opackets[idx] += txq->stats.opackets;
 			tmp.q_obytes[idx] += txq->stats.obytes;
 #endif
-			tmp.q_errors[idx] += txq->stats.odropped;
+			tmp.q_errors[idx] += txq->stats.oerrors;
 		}
 #ifdef MLX5_PMD_SOFT_COUNTERS
 		tmp.opackets += txq->stats.opackets;
 		tmp.obytes += txq->stats.obytes;
 #endif
-		tmp.oerrors += txq->stats.odropped;
+		tmp.oerrors += txq->stats.oerrors;
 	}
 #ifndef MLX5_PMD_SOFT_COUNTERS
 	/* FIXME: retrieve and add hardware counters. */
-- 
2.12.0