We have observed a sudden spike in rx/tx_packets and rx/tx_bytes
reported under /proc/net/dev. There is a race in mlx5e_update_stats()
and some of the get-stats functions (the one that we hit is the
mlx5e_get_stats() which is called by ndo_get_stats64()).
In particular, the very first thing mlx5e_update_sw_counters()
does is 'memset(s, 0, sizeof(*s))'. For example, if mlx5e_get_stats()
is unlucky at one point, rx_bytes and rx_packets could be 0. One second
later, a normal (and much bigger than 0) value will be reported.
This patch is to use a 'struct mlx5e_sw_stats temp' to avoid
a direct memset zero on priv->stats.sw.
mlx5e_update_vport_counters() has a similar race. Hence, addressed
together. However, memset zero is removed instead because
it is not needed.
I am lucky enough to catch this 0-reset in rx multicast:
eth0: 41457665 76804 70 0 0 70 0 47085 15586634
87502 3 0 0 0 3 0
eth0: 41459860 76815 70 0 0 70 0 47094 15588376
87516 3 0 0 0 3 0
eth0: 41460577 76822 70 0 0 70 0 0 15589083
87521 3 0 0 0 3 0
eth0: 41463293 76838 70 0 0 70 0 47108 15595872
87538 3 0 0 0 3 0
eth0: 41463379 76839 70 0 0 70 0 47116 15596138
87539 3 0 0 0 3 0
v2: Remove memset zero from mlx5e_update_vport_counters()
v1: Use temp and memcpy
Fixes: 9218b44dcc05 ("net/mlx5e: Statistics handling refactoring")
Suggested-by: Eric Dumazet <[email protected]>
Suggested-by: Saeed Mahameed <[email protected]>
Signed-off-by: Martin KaFai Lau <[email protected]>
---
drivers/net/ethernet/mellanox/mlx5/core/en_main.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
index 66c133757a5e..15cc7b469d2e 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -174,7 +174,7 @@ static void mlx5e_tx_timeout_work(struct work_struct *work)
static void mlx5e_update_sw_counters(struct mlx5e_priv *priv)
{
- struct mlx5e_sw_stats *s = &priv->stats.sw;
+ struct mlx5e_sw_stats temp, *s = &temp;
struct mlx5e_rq_stats *rq_stats;
struct mlx5e_sq_stats *sq_stats;
u64 tx_offload_none = 0;
@@ -229,6 +229,7 @@ static void mlx5e_update_sw_counters(struct mlx5e_priv
*priv)
s->link_down_events_phy = MLX5_GET(ppcnt_reg,
priv->stats.pport.phy_counters,
counter_set.phys_layer_cntrs.link_down_events);
+ memcpy(&priv->stats.sw, s, sizeof(*s));
}
static void mlx5e_update_vport_counters(struct mlx5e_priv *priv)
@@ -243,7 +244,6 @@ static void mlx5e_update_vport_counters(struct mlx5e_priv
*priv)
MLX5_SET(query_vport_counter_in, in, op_mod, 0);
MLX5_SET(query_vport_counter_in, in, other_vport, 0);
- memset(out, 0, outlen);
mlx5_cmd_exec(mdev, in, sizeof(in), out, outlen);
}
--
2.9.3
