From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.4 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 857FCC433DB for ; Mon, 18 Jan 2021 12:42:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4361F224B8 for ; Mon, 18 Jan 2021 12:42:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404150AbhARMlv (ORCPT ); Mon, 18 Jan 2021 07:41:51 -0500 Received: from szxga07-in.huawei.com ([45.249.212.35]:11401 "EHLO szxga07-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404041AbhARMlr (ORCPT ); Mon, 18 Jan 2021 07:41:47 -0500 Received: from DGGEMS409-HUB.china.huawei.com (unknown [172.30.72.60]) by szxga07-in.huawei.com (SkyGuard) with ESMTP id 4DKBFV05S4z7W9C; Mon, 18 Jan 2021 20:39:58 +0800 (CST) Received: from [127.0.0.1] (10.69.30.204) by DGGEMS409-HUB.china.huawei.com (10.3.19.209) with Microsoft SMTP Server id 14.3.498.0; Mon, 18 Jan 2021 20:40:52 +0800 Subject: Re: [PATCH bpf-next] xsk: build skb by page To: Xuan Zhuo , CC: "Michael S. Tsirkin" , Jason Wang , "David S. Miller" , Jakub Kicinski , =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= , Magnus Karlsson , Jonathan Lemon , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , John Fastabend , Andrii Nakryiko , "Martin KaFai Lau" , Song Liu , Yonghong Song , KP Singh , Willem de Bruijn , Steffen Klassert , Alexander Lobakin , Miaohe Lin , "Mauro Carvalho Chehab" , Antoine Tenart , Michal Kubecek , Andrew Lunn , Florian Fainelli , Meir Lichtinger , , References: <579fa463bba42ac71591540a1811dca41d725350.1610764948.git.xuanzhuo@linux.alibaba.com> From: Yunsheng Lin Message-ID: <4a4b475b-0e79-6cf6-44f5-44d45b5d85b5@huawei.com> Date: Mon, 18 Jan 2021 20:40:52 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: <579fa463bba42ac71591540a1811dca41d725350.1610764948.git.xuanzhuo@linux.alibaba.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.69.30.204] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On 2021/1/16 10:44, Xuan Zhuo wrote: > 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 Does it make sense to use ETHTOOL_TX_COPYBREAK tunable in ethtool to configure if the data is copied or not? > 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% > > Signed-off-by: Xuan Zhuo > Reviewed-by: Dust Li > --- > drivers/net/virtio_net.c | 2 +- > include/linux/netdev_features.h | 5 +- > net/ethtool/common.c | 1 + > net/xdp/xsk.c | 108 +++++++++++++++++++++++++++++++++------- > 4 files changed, 97 insertions(+), 19 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 4ecccb8..841a331 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -2985,7 +2985,7 @@ static int virtnet_probe(struct virtio_device *vdev) > /* Set up network device as normal. */ > dev->priv_flags |= IFF_UNICAST_FLT | IFF_LIVE_ADDR_CHANGE; > dev->netdev_ops = &virtnet_netdev; > - dev->features = NETIF_F_HIGHDMA; > + dev->features = NETIF_F_HIGHDMA | NETIF_F_SKB_NO_LINEAR; > > dev->ethtool_ops = &virtnet_ethtool_ops; > SET_NETDEV_DEV(dev, &vdev->dev); > diff --git a/include/linux/netdev_features.h b/include/linux/netdev_features.h > index 934de56..8dd28e2 100644 > --- a/include/linux/netdev_features.h > +++ b/include/linux/netdev_features.h > @@ -85,9 +85,11 @@ enum { > > NETIF_F_HW_MACSEC_BIT, /* Offload MACsec operations */ > > + NETIF_F_SKB_NO_LINEAR_BIT, /* Allow skb linear is empty */ > + > /* > * Add your fresh new feature above and remember to update > - * netdev_features_strings[] in net/core/ethtool.c and maybe > + * netdev_features_strings[] in net/ethtool/common.c and maybe > * some feature mask #defines below. Please also describe it > * in Documentation/networking/netdev-features.rst. > */ > @@ -157,6 +159,7 @@ enum { > #define NETIF_F_GRO_FRAGLIST __NETIF_F(GRO_FRAGLIST) > #define NETIF_F_GSO_FRAGLIST __NETIF_F(GSO_FRAGLIST) > #define NETIF_F_HW_MACSEC __NETIF_F(HW_MACSEC) > +#define NETIF_F_SKB_NO_LINEAR __NETIF_F(SKB_NO_LINEAR) > > /* Finds the next feature with the highest number of the range of start till 0. > */ > diff --git a/net/ethtool/common.c b/net/ethtool/common.c > index 24036e3..2f3d309 100644 > --- a/net/ethtool/common.c > +++ b/net/ethtool/common.c > @@ -68,6 +68,7 @@ > [NETIF_F_HW_TLS_RX_BIT] = "tls-hw-rx-offload", > [NETIF_F_GRO_FRAGLIST_BIT] = "rx-gro-list", > [NETIF_F_HW_MACSEC_BIT] = "macsec-hw-offload", > + [NETIF_F_SKB_NO_LINEAR_BIT] = "skb-no-linear", > }; > > const char > diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c > index 8037b04..94d17dc 100644 > --- a/net/xdp/xsk.c > +++ b/net/xdp/xsk.c > @@ -430,6 +430,95 @@ static void xsk_destruct_skb(struct sk_buff *skb) > sock_wfree(skb); > } > > +static struct sk_buff *xsk_build_skb_zerocopy(struct xdp_sock *xs, > + struct xdp_desc *desc) > +{ > + u32 len, offset, copy, copied; > + struct sk_buff *skb; > + struct page *page; > + char *buffer; > + int err, i; > + u64 addr; > + > + skb = sock_alloc_send_skb(&xs->sk, 0, 1, &err); > + if (unlikely(!skb)) > + return NULL; > + > + addr = desc->addr; > + len = desc->len; > + > + buffer = xsk_buff_raw_get_data(xs->pool, addr); > + offset = offset_in_page(buffer); > + addr = buffer - (char *)xs->pool->addrs; > + > + for (copied = 0, i = 0; copied < len; ++i) { > + page = xs->pool->umem->pgs[addr >> PAGE_SHIFT]; > + > + get_page(page); > + > + copy = min((u32)(PAGE_SIZE - offset), len - copied); > + > + skb_fill_page_desc(skb, i, page, offset, copy); > + > + copied += copy; > + addr += copy; > + offset = 0; > + } > + > + skb->len += len; > + skb->data_len += len; > + skb->truesize += len; > + > + refcount_add(len, &xs->sk.sk_wmem_alloc); > + > + return skb; > +} > + > +static struct sk_buff *xsk_build_skb(struct xdp_sock *xs, > + struct xdp_desc *desc, int *err) > +{ > + struct sk_buff *skb; > + > + if (xs->dev->features & NETIF_F_SKB_NO_LINEAR) { > + skb = xsk_build_skb_zerocopy(xs, desc); > + if (unlikely(!skb)) { > + *err = -ENOMEM; > + return NULL; > + } > + } else { > + char *buffer; > + u64 addr; > + u32 len; > + int err; > + > + len = desc->len; > + skb = sock_alloc_send_skb(&xs->sk, len, 1, &err); > + if (unlikely(!skb)) { > + *err = -ENOMEM; > + return NULL; > + } > + > + skb_put(skb, len); > + addr = desc->addr; > + buffer = xsk_buff_raw_get_data(xs->pool, desc->addr); > + err = skb_store_bits(skb, 0, buffer, len); > + > + if (unlikely(err)) { > + kfree_skb(skb); > + *err = -EINVAL; > + return NULL; > + } > + } > + > + skb->dev = xs->dev; > + skb->priority = xs->sk.sk_priority; > + skb->mark = xs->sk.sk_mark; > + skb_shinfo(skb)->destructor_arg = (void *)(long)desc->addr; > + skb->destructor = xsk_destruct_skb; > + > + return skb; > +} > + > static int xsk_generic_xmit(struct sock *sk) > { > struct xdp_sock *xs = xdp_sk(sk); > @@ -446,43 +535,28 @@ static int xsk_generic_xmit(struct sock *sk) > goto out; > > while (xskq_cons_peek_desc(xs->tx, &desc, xs->pool)) { > - char *buffer; > - u64 addr; > - u32 len; > - > if (max_batch-- == 0) { > err = -EAGAIN; > goto out; > } > > - len = desc.len; > - skb = sock_alloc_send_skb(sk, len, 1, &err); > + skb = xsk_build_skb(xs, &desc, &err); > if (unlikely(!skb)) > goto out; > > - skb_put(skb, len); > - addr = desc.addr; > - buffer = xsk_buff_raw_get_data(xs->pool, addr); > - err = skb_store_bits(skb, 0, buffer, len); > /* This is the backpressure mechanism for the Tx path. > * Reserve space in the completion queue and only proceed > * if there is space in it. This avoids having to implement > * any buffering in the Tx path. > */ > spin_lock_irqsave(&xs->pool->cq_lock, flags); > - if (unlikely(err) || xskq_prod_reserve(xs->pool->cq)) { > + if (xskq_prod_reserve(xs->pool->cq)) { > spin_unlock_irqrestore(&xs->pool->cq_lock, flags); > kfree_skb(skb); > goto out; > } > spin_unlock_irqrestore(&xs->pool->cq_lock, flags); > > - skb->dev = xs->dev; > - skb->priority = sk->sk_priority; > - skb->mark = sk->sk_mark; > - skb_shinfo(skb)->destructor_arg = (void *)(long)desc.addr; > - skb->destructor = xsk_destruct_skb; > - > err = __dev_direct_xmit(skb, xs->queue_id); > if (err == NETDEV_TX_BUSY) { > /* Tell user-space to retry the send */ >