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[79.177.39.148]) by smtp.gmail.com with ESMTPSA id s1sm35531280wrv.97.2021.01.19.01.50.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 Jan 2021 01:50:34 -0800 (PST) Date: Tue, 19 Jan 2021 04:50:30 -0500 From: "Michael S. Tsirkin" To: Xuan Zhuo Cc: netdev@vger.kernel.org, Jason Wang , "David S. Miller" , Jakub Kicinski , =?iso-8859-1?Q?Bj=F6rn_T=F6pel?= , Magnus Karlsson , Jonathan Lemon , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , John Fastabend , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , KP Singh , virtualization@lists.linux-foundation.org, bpf@vger.kernel.org Subject: Re: [PATCH bpf-next v2 0/3] xsk: build skb by page Message-ID: <20210119045004-mutt-send-email-mst@kernel.org> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, Jan 19, 2021 at 05:45:09PM +0800, Xuan Zhuo wrote: > v2: > 1. add priv_flags IFF_TX_SKB_NO_LINEAR instead of netdev_feature > 2. split the patch to three: > a. add priv_flags IFF_TX_SKB_NO_LINEAR > b. virtio net add priv_flags IFF_TX_SKB_NO_LINEAR > c. When there is support this flag, construct skb without linear space > 3. use ERR_PTR() and PTR_ERR() to handle the err > > > v1 message log: > --------------- > > This patch is used to construct skb based on page to save memory copy > overhead. > > This has one problem: > > We construct the skb by fill the data page as a frag into the skb. In > this way, the linear space is empty, and the header information is also > in the frag, not in the linear space, which is not allowed for some > network cards. For example, Mellanox Technologies MT27710 Family > [ConnectX-4 Lx] will get the following error message: > > mlx5_core 0000:3b:00.1 eth1: Error cqe on cqn 0x817, ci 0x8, qn 0x1dbb, opcode 0xd, syndrome 0x1, vendor syndrome 0x68 > 00000000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00000010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00000020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00000030: 00 00 00 00 60 10 68 01 0a 00 1d bb 00 0f 9f d2 > WQE DUMP: WQ size 1024 WQ cur size 0, WQE index 0xf, len: 64 > 00000000: 00 00 0f 0a 00 1d bb 03 00 00 00 08 00 00 00 00 > 00000010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00000020: 00 00 00 2b 00 08 00 00 00 00 00 05 9e e3 08 00 > 00000030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > mlx5_core 0000:3b:00.1 eth1: ERR CQE on SQ: 0x1dbb > > I also tried to use build_skb to construct skb, but because of the > existence of skb_shinfo, it must be behind the linear space, so this > method is not working. We can't put skb_shinfo on desc->addr, it will be > exposed to users, this is not safe. > > Finally, I added a feature NETIF_F_SKB_NO_LINEAR to identify whether the > network card supports the header information of the packet in the frag > and not in the linear space. > > ---------------- Performance Testing ------------ > > The test environment is Aliyun ECS server. > Test cmd: > ``` > xdpsock -i eth0 -t -S -s > ``` > > Test result data: > > size 64 512 1024 1500 > copy 1916747 1775988 1600203 1440054 > page 1974058 1953655 1945463 1904478 > percent 3.0% 10.0% 21.58% 32.3% Just making sure, are these test results with v2? > > Xuan Zhuo (3): > net: add priv_flags for allow tx skb without linear > virtio-net: support IFF_TX_SKB_NO_LINEAR > xsk: build skb by page > > drivers/net/virtio_net.c | 3 +- > include/linux/netdevice.h | 3 ++ > net/xdp/xsk.c | 112 ++++++++++++++++++++++++++++++++++++++-------- > 3 files changed, 99 insertions(+), 19 deletions(-) > > -- > 1.8.3.1