netdev - Re: [PATCH net-next v8 3/6] net: napi: add CPU affinity to napi

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Message-ID: <738fed19-378f-4aa9-8d42-5c18b8ea321d@redhat.com>
Date: Thu, 13 Feb 2025 13:26:34 +0100
From: Paolo Abeni <pabeni@...hat.com>
To: Ahmed Zaki <ahmed.zaki@...el.com>, netdev@...r.kernel.org
Cc: intel-wired-lan@...ts.osuosl.org, andrew+netdev@...n.ch,
 edumazet@...gle.com, kuba@...nel.org, horms@...nel.org, davem@...emloft.net,
 michael.chan@...adcom.com, tariqt@...dia.com, anthony.l.nguyen@...el.com,
 przemyslaw.kitszel@...el.com, jdamato@...tly.com, shayd@...dia.com,
 akpm@...ux-foundation.org, shayagr@...zon.com,
 kalesh-anakkur.purayil@...adcom.com, pavan.chebbi@...adcom.com
Subject: Re: [PATCH net-next v8 3/6] net: napi: add CPU affinity to
 napi_config

On 2/11/25 10:06 PM, Ahmed Zaki wrote:
> @@ -394,10 +395,8 @@ struct napi_struct {
>  	struct list_head	dev_list;
>  	struct hlist_node	napi_hash_node;
>  	int			irq;
> -#ifdef CONFIG_RFS_ACCEL
>  	struct irq_affinity_notify notify;
>  	int			napi_rmap_idx;
> -#endif

I'm sorry for the late doubt, but it's not clear to me why you need to
add the #ifdef in the previous patch ?!?

> diff --git a/net/core/dev.c b/net/core/dev.c
> index 209296cef3cd..d2c942bbd5e6 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -6871,28 +6871,39 @@ void netif_queue_set_napi(struct net_device *dev, unsigned int queue_index,
>  }
>  EXPORT_SYMBOL(netif_queue_set_napi);
>  
> -#ifdef CONFIG_RFS_ACCEL
>  static void
> -netif_irq_cpu_rmap_notify(struct irq_affinity_notify *notify,
> -			  const cpumask_t *mask)
> +netif_napi_irq_notify(struct irq_affinity_notify *notify,
> +		      const cpumask_t *mask)
>  {
>  	struct napi_struct *napi =
>  		container_of(notify, struct napi_struct, notify);
> +#ifdef CONFIG_RFS_ACCEL
>  	struct cpu_rmap *rmap = napi->dev->rx_cpu_rmap;
>  	int err;
> +#endif
>  
> -	err = cpu_rmap_update(rmap, napi->napi_rmap_idx, mask);
> -	if (err)
> -		netdev_warn(napi->dev, "RMAP update failed (%d)\n",
> -			    err);
> +	if (napi->config && napi->dev->irq_affinity_auto)
> +		cpumask_copy(&napi->config->affinity_mask, mask);
> +
> +#ifdef CONFIG_RFS_ACCEL
> +	if (napi->dev->rx_cpu_rmap_auto) {
> +		err = cpu_rmap_update(rmap, napi->napi_rmap_idx, mask);
> +		if (err)
> +			netdev_warn(napi->dev, "RMAP update failed (%d)\n",
> +				    err);
> +	}
> +#endif

Minor nit: if you provide a netif_rx_cpu_rmap() helper returning
dev->rx_cpu_rmap or NULL for !CONFIG_RFS_ACCEL build, you can avoid the
above 2 ifdefs and possibly more below.

> @@ -6915,7 +6926,6 @@ static int napi_irq_cpu_rmap_add(struct napi_struct *napi, int irq)
>  	if (rc)
>  		goto err_set;
>  
> -	set_bit(NAPI_STATE_HAS_NOTIFIER, &napi->state);

Minor nit: I think it would be better if the previous patch would add
directly this line in netif_napi_set_irq_locked() (avoding the removal
here).

/P