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[73.158.218.242]) by smtp.gmail.com with UTF8SMTPSA id 98e67ed59e1d1-3158a2f3358sm4779624a91.30.2025.06.20.07.25.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 20 Jun 2025 07:25:55 -0700 (PDT) Date: Fri, 20 Jun 2025 07:25:54 -0700 From: Stanislav Fomichev To: Jakub Kicinski Cc: Jason Xing , davem@davemloft.net, edumazet@google.com, pabeni@redhat.com, bjorn@kernel.org, magnus.karlsson@intel.com, maciej.fijalkowski@intel.com, jonathan.lemon@gmail.com, sdf@fomichev.me, ast@kernel.org, daniel@iogearbox.net, hawk@kernel.org, john.fastabend@gmail.com, joe@dama.to, willemdebruijn.kernel@gmail.com, bpf@vger.kernel.org, netdev@vger.kernel.org, Jason Xing Subject: Re: [PATCH net-next v3] net: xsk: introduce XDP_MAX_TX_BUDGET set/getsockopt Message-ID: References: <20250619090440.65509-1-kerneljasonxing@gmail.com> <20250619080904.0a70574c@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20250619080904.0a70574c@kernel.org> On 06/19, Jakub Kicinski wrote: > 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? 1) xsk_tx_peek_desc is for zc case and xsk_build_skb is copy mode; whether we want to affect zc case given the fact that Jason seemingly cares about copy mode is a good question. 2) I do find it surprising as well. Recent busy polling patches were also using/targeting copy mode. But from my pow, if people use it, I see no reason to make it more usable.