[dpdk-dev] [PATCH] mlx5: Report imissed stat

[Tom Barbette <barbette@kth.se>]

The imissed counters (number of packets dropped because the queues were
full) were actually reported through xstats as "rx_out_of_buffer"
but was not reported through stats.

Following a recent discussion on the ML, as there is no way to tell the
user if a counter is implemented or not, this should be considered a
bug. Eg, user looking at imissed will think the packets are lost before
reaching the device.

As for xstats, I added a base counter to be able to "reset" imissed.

Signed-off-by: Tom Barbette <barbette@kth.se>
---
 drivers/net/mlx5/mlx5.h       |  2 ++
 drivers/net/mlx5/mlx5_stats.c | 36 +++++++++++++++++++++++-------------
 2 files changed, 25 insertions(+), 13 deletions(-)

diff --git a/drivers/net/mlx5/mlx5.h b/drivers/net/mlx5/mlx5.h
index a3a34cf..61054a8 100644
--- a/drivers/net/mlx5/mlx5.h
+++ b/drivers/net/mlx5/mlx5.h
@@ -77,6 +77,8 @@ struct mlx5_xstats_ctrl {
 	/* Index in the device counters table. */
 	uint16_t dev_table_idx[MLX5_MAX_XSTATS];
 	uint64_t base[MLX5_MAX_XSTATS];
+	/* Base for imissed counter. */
+	uint64_t imissed_base;
 };
 
 /* Flow list . */
diff --git a/drivers/net/mlx5/mlx5_stats.c b/drivers/net/mlx5/mlx5_stats.c
index 91f3d47..1e75e85 100644
--- a/drivers/net/mlx5/mlx5_stats.c
+++ b/drivers/net/mlx5/mlx5_stats.c
@@ -119,6 +119,24 @@ static const struct mlx5_counter_ctrl mlx5_counters_init[] = {
 
 static const unsigned int xstats_n = RTE_DIM(mlx5_counters_init);
 
+static inline void
+mlx5_read_ib_stat(struct priv *priv, unsigned int idx, uint64_t *stat)
+{
+	FILE *file;
+	MKSTR(path, "%s/ports/1/hw_counters/%s",
+		  priv->ibdev_path,
+		  mlx5_counters_init[idx].ctr_name);
+
+	file = fopen(path, "rb");
+	if (file) {
+		int n = fscanf(file, "%" SCNu64, stat);
+
+		fclose(file);
+		if (n != 1)
+			stat = 0;
+	}
+}
+
 /**
  * Read device counters table.
  *
@@ -155,19 +173,7 @@ mlx5_read_dev_counters(struct rte_eth_dev *dev, uint64_t *stats)
 	}
 	for (i = 0; i != xstats_n; ++i) {
 		if (mlx5_counters_init[i].ib) {
-			FILE *file;
-			MKSTR(path, "%s/ports/1/hw_counters/%s",
-			      priv->ibdev_path,
-			      mlx5_counters_init[i].ctr_name);
-
-			file = fopen(path, "rb");
-			if (file) {
-				int n = fscanf(file, "%" SCNu64, &stats[i]);
-
-				fclose(file);
-				if (n != 1)
-					stats[i] = 0;
-			}
+			mlx5_read_ib_stat(priv, i, &stats[i]);
 		} else {
 			stats[i] = (uint64_t)
 				et_stats->data[xstats_ctrl->dev_table_idx[i]];
@@ -281,6 +287,7 @@ mlx5_xstats_init(struct rte_eth_dev *dev)
 	if (ret)
 		DRV_LOG(ERR, "port %u cannot read device counters: %s",
 			dev->data->port_id, strerror(rte_errno));
+	mlx5_read_ib_stat(priv, 17, &xstats_ctrl->imissed_base);
 free:
 	rte_free(strings);
 }
@@ -389,6 +396,8 @@ mlx5_stats_get(struct rte_eth_dev *dev, struct rte_eth_stats *stats)
 #endif
 		tmp.oerrors += txq->stats.oerrors;
 	}
+	mlx5_read_ib_stat(priv, 17, &tmp.imissed);
+	tmp.imissed -= priv->xstats_ctrl.imissed_base;
 #ifndef MLX5_PMD_SOFT_COUNTERS
 	/* FIXME: retrieve and add hardware counters. */
 #endif
@@ -461,6 +470,7 @@ mlx5_xstats_reset(struct rte_eth_dev *dev)
 	}
 	for (i = 0; i != n; ++i)
 		xstats_ctrl->base[i] = counters[i];
+	mlx5_read_ib_stat(priv, 17, &xstats_ctrl->imissed_base);
 }
 
 /**
-- 
2.7.4