Re: [PATCH] net/core: Export dev_core_stats_rx_dropped_inc sets

[Eric Dumazet]

On Mon, Sep 11, 2023 at 10:20 AM Yajun Deng <yajun.deng@xxxxxxxxx> wrote:
>
> Although there is a kfree_skb_reason() helper function that can be used
> to find the reason for dropped packets, but most callers didn't increase
> one of rx_dropped, tx_dropped, rx_nohandler and rx_otherhost_dropped.
>
> For the users, people are more concerned about why the dropped in ifconfig
> is increasing. So we can export dev_core_stats_rx_dropped_inc sets,
> which users would trace them know why rx_dropped is increasing.
>
> Export dev_core_stats_{rx_dropped, tx_dropped, rx_nohandler,
> rx_otherhost_dropped}_inc for trace. Also, move dev_core_stats()
> and netdev_core_stats_alloc() in dev.c, because they are not called
> externally.
>
> Signed-off-by: Yajun Deng <yajun.deng@xxxxxxxxx>

Okay, but it seems you forgot to say which tree was targeted by this patch.

Documentation/process/maintainer-netdev.rst

I would guess net-next, but patch authors are supposed to be explicit.

> ---
>  include/linux/netdevice.h | 32 +++++---------------------------
>  net/core/dev.c            | 30 ++++++++++++++++++++++++++++--
>  2 files changed, 33 insertions(+), 29 deletions(-)
>
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index 0896aaa91dd7..879b01c85ba4 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -3954,6 +3954,11 @@ int dev_forward_skb_nomtu(struct net_device *dev, struct sk_buff *skb);
>  bool is_skb_forwardable(const struct net_device *dev,
>                         const struct sk_buff *skb);
>
> +void dev_core_stats_rx_dropped_inc(struct net_device *dev);
> +void dev_core_stats_tx_dropped_inc(struct net_device *dev);
> +void dev_core_stats_rx_nohandler_inc(struct net_device *dev);
> +void dev_core_stats_rx_otherhost_dropped_inc(struct net_device *dev);
> +
>  static __always_inline bool __is_skb_forwardable(const struct net_device *dev,
>                                                  const struct sk_buff *skb,
>                                                  const bool check_mtu)
> @@ -3980,33 +3985,6 @@ static __always_inline bool __is_skb_forwardable(const struct net_device *dev,
>         return false;
>  }
>
> -struct net_device_core_stats __percpu *netdev_core_stats_alloc(struct net_device *dev);
> -
> -static inline struct net_device_core_stats __percpu *dev_core_stats(struct net_device *dev)
> -{
> -       /* This READ_ONCE() pairs with the write in netdev_core_stats_alloc() */
> -       struct net_device_core_stats __percpu *p = READ_ONCE(dev->core_stats);
> -
> -       if (likely(p))
> -               return p;
> -
> -       return netdev_core_stats_alloc(dev);
> -}
> -
> -#define DEV_CORE_STATS_INC(FIELD)                                              \
> -static inline void dev_core_stats_##FIELD##_inc(struct net_device *dev)                \
> -{                                                                              \
> -       struct net_device_core_stats __percpu *p;                               \
> -                                                                               \
> -       p = dev_core_stats(dev);                                                \
> -       if (p)                                                                  \
> -               this_cpu_inc(p->FIELD);                                         \
> -}
> -DEV_CORE_STATS_INC(rx_dropped)
> -DEV_CORE_STATS_INC(tx_dropped)
> -DEV_CORE_STATS_INC(rx_nohandler)
> -DEV_CORE_STATS_INC(rx_otherhost_dropped)
> -
>  static __always_inline int ____dev_forward_skb(struct net_device *dev,
>                                                struct sk_buff *skb,
>                                                const bool check_mtu)
> diff --git a/net/core/dev.c b/net/core/dev.c
> index ccff2b6ef958..32ba730405b4 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -10475,7 +10475,7 @@ void netdev_stats_to_stats64(struct rtnl_link_stats64 *stats64,
>  }
>  EXPORT_SYMBOL(netdev_stats_to_stats64);
>
> -struct net_device_core_stats __percpu *netdev_core_stats_alloc(struct net_device *dev)
> +static struct net_device_core_stats __percpu *netdev_core_stats_alloc(struct net_device *dev)
>  {
>         struct net_device_core_stats __percpu *p;
>
> @@ -10488,7 +10488,33 @@ struct net_device_core_stats __percpu *netdev_core_stats_alloc(struct net_device
>         /* This READ_ONCE() pairs with the cmpxchg() above */
>         return READ_ONCE(dev->core_stats);
>  }
> -EXPORT_SYMBOL(netdev_core_stats_alloc);
> +
> +static inline struct net_device_core_stats __percpu *dev_core_stats(struct net_device *dev)

Please remove this inline attritbute. Consider using __cold instead.

> +{
> +       /* This READ_ONCE() pairs with the write in netdev_core_stats_alloc() */
> +       struct net_device_core_stats __percpu *p = READ_ONCE(dev->core_stats);
> +
> +       if (likely(p))
> +               return p;
> +
> +       return netdev_core_stats_alloc(dev);
> +}
> +
> +#define DEV_CORE_STATS_INC(FIELD)                              \
> +void dev_core_stats_##FIELD##_inc(struct net_device *dev)      \
> +{                                                              \
> +       struct net_device_core_stats __percpu *p;               \
> +                                                               \
> +       p = dev_core_stats(dev);                                \
> +       if (p)                                                  \
> +               this_cpu_inc(p->FIELD);                         \
> +}                                                              \
> +EXPORT_SYMBOL(dev_core_stats_##FIELD##_inc)
> +
> +DEV_CORE_STATS_INC(rx_dropped);
> +DEV_CORE_STATS_INC(tx_dropped);
> +DEV_CORE_STATS_INC(rx_nohandler);
> +DEV_CORE_STATS_INC(rx_otherhost_dropped);

#undef DEV_CORE_STATS_INC

>
>  /**
>   *     dev_get_stats   - get network device statistics
> --
> 2.25.1
>