netdev - Re: [PATCH net-next v2 6/9] xsk: add direct xmit in batch function

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Message-ID: <aKyev6DadDuL3Xlo@mini-arch>
Date: Mon, 25 Aug 2025 10:34:55 -0700
From: Stanislav Fomichev <stfomichev@...il.com>
To: Jason Xing <kerneljasonxing@...il.com>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
	pabeni@...hat.com, bjorn@...nel.org, magnus.karlsson@...el.com,
	maciej.fijalkowski@...el.com, jonathan.lemon@...il.com,
	sdf@...ichev.me, ast@...nel.org, daniel@...earbox.net,
	hawk@...nel.org, john.fastabend@...il.com, horms@...nel.org,
	andrew+netdev@...n.ch, bpf@...r.kernel.org, netdev@...r.kernel.org,
	Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH net-next v2 6/9] xsk: add direct xmit in batch function

On 08/25, Jason Xing wrote:
> From: Jason Xing <kernelxing@...cent.com>
> 
> Add batch xmit logic.
> 
> Only grabbing the lock and disable bottom half once and sent all
> the aggregated packets in one loop.
> 
> Since previous patch puts descriptors in xs->skb_cache in a reversed
> order, this patch sends each skb out from start to end when 'start' is
> not smaller than 'end'.
> 
> Signed-off-by: Jason Xing <kernelxing@...cent.com>
> ---
>  include/linux/netdevice.h |  3 +++
>  net/core/dev.c            | 19 +++++++++++++++++++
>  2 files changed, 22 insertions(+)
> 
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index 5e5de4b0a433..8e2688e3f2e4 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -3352,6 +3352,9 @@ u16 dev_pick_tx_zero(struct net_device *dev, struct sk_buff *skb,
>  
>  int __dev_queue_xmit(struct sk_buff *skb, struct net_device *sb_dev);
>  int __dev_direct_xmit(struct sk_buff *skb, u16 queue_id);
> +int xsk_direct_xmit_batch(struct sk_buff **skbs, struct net_device *dev,
> +			  struct netdev_queue *txq, int *cur,
> +			  int start, int end);
>  
>  static inline int dev_queue_xmit(struct sk_buff *skb)
>  {
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 68dc47d7e700..a5a6b9a199e9 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -4742,6 +4742,25 @@ int __dev_queue_xmit(struct sk_buff *skb, struct net_device *sb_dev)
>  }
>  EXPORT_SYMBOL(__dev_queue_xmit);
>  
> +int xsk_direct_xmit_batch(struct sk_buff **skbs, struct net_device *dev,
> +			  struct netdev_queue *txq, int *cur,
> +			  int start, int end)
> +{
> +	int ret = NETDEV_TX_BUSY;
> +
> +	local_bh_disable();
> +	HARD_TX_LOCK(dev, txq, smp_processor_id());
> +	for (*cur = start; *cur >= end; (*cur)--) {

skbs support chaining (via list member), any reason not to use that for
batching purposes?