Re: [net-next v5 5/9] net: napi: Add napi_config

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On Wed, Oct 9, 2024 at 2:56 AM Joe Damato <jdamato@xxxxxxxxxx> wrote:
>
> Add a persistent NAPI config area for NAPI configuration to the core.
> Drivers opt-in to setting the persistent config for a NAPI by passing an
> index when calling netif_napi_add_config.
>
> napi_config is allocated in alloc_netdev_mqs, freed in free_netdev
> (after the NAPIs are deleted).
>
> Drivers which call netif_napi_add_config will have persistent per-NAPI
> settings: NAPI IDs, gro_flush_timeout, and defer_hard_irq settings.
>
> Per-NAPI settings are saved in napi_disable and restored in napi_enable.
>
> Co-developed-by: Martin Karsten <mkarsten@xxxxxxxxxxxx>
> Signed-off-by: Martin Karsten <mkarsten@xxxxxxxxxxxx>
> Signed-off-by: Joe Damato <jdamato@xxxxxxxxxx>
> ---
>  .../networking/net_cachelines/net_device.rst  |  1 +
>  include/linux/netdevice.h                     | 36 ++++++++-
>  net/core/dev.c                                | 79 +++++++++++++++++--
>  net/core/dev.h                                | 12 +++
>  4 files changed, 118 insertions(+), 10 deletions(-)
>
> diff --git a/Documentation/networking/net_cachelines/net_device.rst b/Documentation/networking/net_cachelines/net_device.rst
> index 3ab663b6cf16..9d86720cb722 100644
> --- a/Documentation/networking/net_cachelines/net_device.rst
> +++ b/Documentation/networking/net_cachelines/net_device.rst
> @@ -183,5 +183,6 @@ struct_dpll_pin*                    dpll_pin
>  struct hlist_head                   page_pools
>  struct dim_irq_moder*               irq_moder
>  u64                                 max_pacing_offload_horizon
> +struct_napi_config*                 napi_config
>  unsigned_long                       gro_flush_timeout
>  u32                                 napi_defer_hard_irqs
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index 4239a4a9d295..b65a901ab4e7 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -342,6 +342,15 @@ struct gro_list {
>   */
>  #define GRO_HASH_BUCKETS       8
>
> +/*
> + * Structure for per-NAPI config
> + */
> +struct napi_config {
> +       u64 gro_flush_timeout;
> +       u32 defer_hard_irqs;
> +       unsigned int napi_id;
> +};
> +
>  /*
>   * Structure for NAPI scheduling similar to tasklet but with weighting
>   */
> @@ -379,6 +388,8 @@ struct napi_struct {
>         struct list_head        dev_list;
>         struct hlist_node       napi_hash_node;
>         int                     irq;
> +       int                     index;
> +       struct napi_config      *config;
>  };
>
>  enum {
> @@ -1860,9 +1871,6 @@ enum netdev_reg_state {
>   *                             allocated at register_netdev() time
>   *     @real_num_rx_queues:    Number of RX queues currently active in device
>   *     @xdp_prog:              XDP sockets filter program pointer
> - *     @gro_flush_timeout:     timeout for GRO layer in NAPI
> - *     @napi_defer_hard_irqs:  If not zero, provides a counter that would
> - *                             allow to avoid NIC hard IRQ, on busy queues.
>   *
>   *     @rx_handler:            handler for received packets
>   *     @rx_handler_data:       XXX: need comments on this one
> @@ -2012,6 +2020,11 @@ enum netdev_reg_state {
>   *                where the clock is recovered.
>   *
>   *     @max_pacing_offload_horizon: max EDT offload horizon in nsec.
> + *     @napi_config: An array of napi_config structures containing per-NAPI
> + *                   settings.
> + *     @gro_flush_timeout:     timeout for GRO layer in NAPI
> + *     @napi_defer_hard_irqs:  If not zero, provides a counter that would
> + *                             allow to avoid NIC hard IRQ, on busy queues.
>   *
>   *     FIXME: cleanup struct net_device such that network protocol info
>   *     moves out.
> @@ -2405,6 +2418,7 @@ struct net_device {
>         struct dim_irq_moder    *irq_moder;
>
>         u64                     max_pacing_offload_horizon;
> +       struct napi_config      *napi_config;
>         unsigned long           gro_flush_timeout;
>         u32                     napi_defer_hard_irqs;
>
> @@ -2657,6 +2671,22 @@ netif_napi_add_tx_weight(struct net_device *dev,
>         netif_napi_add_weight(dev, napi, poll, weight);
>  }
>
> +/**
> + * netif_napi_add_config - initialize a NAPI context with persistent config
> + * @dev: network device
> + * @napi: NAPI context
> + * @poll: polling function
> + * @index: the NAPI index
> + */
> +static inline void
> +netif_napi_add_config(struct net_device *dev, struct napi_struct *napi,
> +                     int (*poll)(struct napi_struct *, int), int index)
> +{
> +       napi->index = index;
> +       napi->config = &dev->napi_config[index];
> +       netif_napi_add_weight(dev, napi, poll, NAPI_POLL_WEIGHT);
> +}
> +
>  /**
>   * netif_napi_add_tx() - initialize a NAPI context to be used for Tx only
>   * @dev:  network device
> diff --git a/net/core/dev.c b/net/core/dev.c
> index fca2295f4d95..bd87232f7b37 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -6503,6 +6503,22 @@ EXPORT_SYMBOL(napi_busy_loop);
>
>  #endif /* CONFIG_NET_RX_BUSY_POLL */
>
> +static void __napi_hash_add_with_id(struct napi_struct *napi,
> +                                   unsigned int napi_id)
> +{
> +       napi->napi_id = napi_id;
> +       hlist_add_head_rcu(&napi->napi_hash_node,
> +                          &napi_hash[napi->napi_id % HASH_SIZE(napi_hash)]);
> +}
> +
> +static void napi_hash_add_with_id(struct napi_struct *napi,
> +                                 unsigned int napi_id)
> +{
> +       spin_lock(&napi_hash_lock);
> +       __napi_hash_add_with_id(napi, napi_id);

Hmmm... there is no check if 'napi_id' is already used and hashed.

I would add

WARN_ON_ONCE(napi_by_id(napi_id));

> +       spin_unlock(&napi_hash_lock);
> +}
> +
>  static void napi_hash_add(struct napi_struct *napi)
>  {
>         if (test_bit(NAPI_STATE_NO_BUSY_POLL, &napi->state))
> @@ -6515,10 +6531,8 @@ static void napi_hash_add(struct napi_struct *napi)
>                 if (unlikely(++napi_gen_id < MIN_NAPI_ID))
>                         napi_gen_id = MIN_NAPI_ID;
>         } while (napi_by_id(napi_gen_id));
> -       napi->napi_id = napi_gen_id;
>
> -       hlist_add_head_rcu(&napi->napi_hash_node,
> -                          &napi_hash[napi->napi_id % HASH_SIZE(napi_hash)]);
> +       __napi_hash_add_with_id(napi, napi_gen_id);
>
>         spin_unlock(&napi_hash_lock);
>  }
>





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