On Fri, Apr 21, 2017 at 7:40 AM, Martin KaFai Lau <ka...@fb.com> wrote:
> 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 <eric.duma...@gmail.com>
> Suggested-by: Saeed Mahameed <sae...@mellanox.com>
> Signed-off-by: Martin KaFai Lau <ka...@fb.com>
> ---
Thank you Martin and Eric for the fix, we will follow up with the
spinlock fix soon.
Acked-by: Saeed Mahameed <sae...@mellanox.com>
