netdev - Re: [PATCH net-next v3] net: xsk: introduce XDP_MAX_TX

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Message-ID: <20250619080904.0a70574c@kernel.org>
Date: Thu, 19 Jun 2025 08:09:04 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Jason Xing <kerneljasonxing@...il.com>
Cc: davem@...emloft.net, edumazet@...gle.com, 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,
 joe@...a.to, willemdebruijn.kernel@...il.com, bpf@...r.kernel.org,
 netdev@...r.kernel.org, Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH net-next v3] net: xsk: introduce XDP_MAX_TX_BUDGET
 set/getsockopt

On Thu, 19 Jun 2025 17:04:40 +0800 Jason Xing wrote:
> @@ -424,7 +421,9 @@ bool xsk_tx_peek_desc(struct xsk_buff_pool *pool, struct xdp_desc *desc)
>  	rcu_read_lock();
>  again:
>  	list_for_each_entry_rcu(xs, &pool->xsk_tx_list, tx_list) {
> -		if (xs->tx_budget_spent >= MAX_PER_SOCKET_BUDGET) {
> +		int max_budget = READ_ONCE(xs->max_tx_budget);
> +
> +		if (xs->tx_budget_spent >= max_budget) {
>  			budget_exhausted = true;
>  			continue;
>  		}
> @@ -779,7 +778,7 @@ static struct sk_buff *xsk_build_skb(struct xdp_sock *xs,
>  static int __xsk_generic_xmit(struct sock *sk)
>  {
>  	struct xdp_sock *xs = xdp_sk(sk);
> -	u32 max_batch = TX_BATCH_SIZE;
> +	u32 max_budget = READ_ONCE(xs->max_tx_budget);

Hm, maybe a question to Stan / Willem & other XSK experts but are these
two max values / code paths really related? Question 2 -- is generic
XSK a legit optimization target, legit enough to add uAPI?

Jason, I think some additions to Documentation/ and quantification of
the benefits would be needed as well.
-- 
pw-bot: cr