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[34.86.148.56]) by smtp.gmail.com with ESMTPSA id qp11-20020a056214598b00b0068fef74fdb3sm2137813qvb.59.2024.03.01.10.40.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 01 Mar 2024 10:40:46 -0800 (PST) Date: Fri, 01 Mar 2024 13:40:46 -0500 From: Willem de Bruijn To: Maciej Fijalkowski , Yunjian Wang Cc: mst@redhat.com, willemdebruijn.kernel@gmail.com, jasowang@redhat.com, kuba@kernel.org, bjorn@kernel.org, magnus.karlsson@intel.com, jonathan.lemon@gmail.com, davem@davemloft.net, bpf@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux.dev, xudingke@huawei.com, liwei395@huawei.com Message-ID: <65e2212e66769_158220294f@willemb.c.googlers.com.notmuch> In-Reply-To: References: <1709118356-133960-1-git-send-email-wangyunjian@huawei.com> Subject: Re: [PATCH net-next v2 3/3] tun: AF_XDP Tx zero-copy support Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Maciej Fijalkowski wrote: > On Wed, Feb 28, 2024 at 07:05:56PM +0800, Yunjian Wang wrote: > > This patch set allows TUN to support the AF_XDP Tx zero-copy feature, > > which can significantly reduce CPU utilization for XDP programs. > > Why no Rx ZC support though? What will happen if I try rxdrop xdpsock > against tun with this patch? You clearly allow for that. This is AF_XDP receive zerocopy, right? The naming is always confusing with tun, but even though from a tun PoV this happens on ndo_start_xmit, it is the AF_XDP equivalent to tun_put_user. So the implementation is more like other device's Rx ZC. I would have preferred that name, but I think Jason asked for this and given tun's weird status, there is something bo said for either.