netdev - Re: [PATCH net-next] netdevice: move xdp_rxq within netdev_rx

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Date:   Mon, 23 Aug 2021 20:38:12 +0200
From:   Jesper Dangaard Brouer <jbrouer@...hat.com>
To:     Jakub Kicinski <kuba@...nel.org>, davem@...emloft.net
Cc:     brouer@...hat.com, netdev@...r.kernel.org, bpf@...r.kernel.org,
        magnus.karlsson@...el.com
Subject: Re: [PATCH net-next] netdevice: move xdp_rxq within netdev_rx_queue



On 23/08/2021 20.01, Jakub Kicinski wrote:
> Both struct netdev_rx_queue and struct xdp_rxq_info are cacheline
> aligned. This causes extra padding before and after the xdp_rxq
> member. Move the member upfront, so that it's naturally aligned.
> 
> Before:
> 	/* size: 256, cachelines: 4, members: 6 */
> 	/* sum members: 160, holes: 1, sum holes: 40 */
> 	/* padding: 56 */
> 	/* paddings: 1, sum paddings: 36 */
> 	/* forced alignments: 1, forced holes: 1, sum forced holes: 40 */
> 
> After:
> 	/* size: 192, cachelines: 3, members: 6 */
> 	/* padding: 32 */
> 	/* paddings: 1, sum paddings: 36 */
> 	/* forced alignments: 1 */
> 
> Signed-off-by: Jakub Kicinski <kuba@...nel.org>
> ---
>   include/linux/netdevice.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)


LGTM

Acked-by: Jesper Dangaard Brouer <brouer@...hat.com>

> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index 9579942ac2fd..514ec3a0507c 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -722,13 +722,13 @@ bool rps_may_expire_flow(struct net_device *dev, u16 rxq_index, u32 flow_id,
>   
>   /* This structure contains an instance of an RX queue. */
>   struct netdev_rx_queue {
> +	struct xdp_rxq_info		xdp_rxq;
>   #ifdef CONFIG_RPS
>   	struct rps_map __rcu		*rps_map;
>   	struct rps_dev_flow_table __rcu	*rps_flow_table;
>   #endif
>   	struct kobject			kobj;
>   	struct net_device		*dev;
> -	struct xdp_rxq_info		xdp_rxq;
>   #ifdef CONFIG_XDP_SOCKETS
>   	struct xsk_buff_pool            *pool;
>   #endif
>