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[23.128.96.18]) by mx.google.com with ESMTP id dd11si1556777edb.36.2021.01.18.20.36.30; Mon, 18 Jan 2021 20:36:54 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@pm.me header.s=protonmail header.b=BFjNJjDc; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=pm.me Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2405039AbhAROpc (ORCPT + 99 others); Mon, 18 Jan 2021 09:45:32 -0500 Received: from mail-40133.protonmail.ch ([185.70.40.133]:17076 "EHLO mail-40133.protonmail.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404931AbhAROll (ORCPT ); Mon, 18 Jan 2021 09:41:41 -0500 Date: Mon, 18 Jan 2021 14:40:41 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=pm.me; s=protonmail; t=1610980853; bh=sT4qH+o/dm1Su+f+vO2M5l0wLdLF5/1KpnEkQpaAXs4=; h=Date:To:From:Cc:Reply-To:Subject:In-Reply-To:References:From; b=BFjNJjDca831d3Ck1vHWE5jVuQfjnDTbBT/RA+vhBrKMYJ4fQYede/It+coyIxFuk aVognhgUoOHEXnwNtLXK3IMDFVNWlLRwRdh9NcHCHdsN+dILQkTmrZ7sWuVudA77x+ pc6rsrz8NhD5e8DZQhwijzvXzR2WngdWH8VWkZYeZLNBIff+BzCjThXpuwXtWhyGo6 ACpoByB7GmR+Ps9quChQ8ChqNN7AvPfuI7wNP8sylv9kqbY9PuecJooLkBMGu67Ys9 mZKBZ9pA/bJHMrkvmShNaHCvBflmT0+aZEGQ2VYXMSGaU8vad7LW+OH7oyEeMiptRZ HG7J3Q9yfTU0w== To: Yunsheng Lin From: Alexander Lobakin Cc: Alexander Lobakin , Xuan Zhuo , "Michael S. Tsirkin" , Jason Wang , "David S. Miller" , Jakub Kicinski , bjorn.topel@intel.com, 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 , Miaohe Lin , Mauro Carvalho Chehab , Antoine Tenart , Michal Kubecek , Andrew Lunn , Florian Fainelli , Meir Lichtinger , virtualization@lists.linux-foundation.org, bpf@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Reply-To: Alexander Lobakin Subject: Re: [PATCH bpf-next] xsk: build skb by page Message-ID: <20210118143948.8706-1-alobakin@pm.me> In-Reply-To: <20210118125937.4088-1-alobakin@pm.me> References: <579fa463bba42ac71591540a1811dca41d725350.1610764948.git.xuanzhuo@linux.alibaba.com> <4a4b475b-0e79-6cf6-44f5-44d45b5d85b5@huawei.com> <20210118125937.4088-1-alobakin@pm.me> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Spam-Status: No, score=-1.2 required=10.0 tests=ALL_TRUSTED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF shortcircuit=no autolearn=disabled version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on mailout.protonmail.ch Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Alexander Lobakin Date: Mon, 18 Jan 2021 13:00:17 +0000 > From: Yunsheng Lin > Date: Mon, 18 Jan 2021 20:40:52 +0800 > >> 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 0x1= dbb, 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 b= e >>> exposed to users, this is not safe. >>> >>> Finally, I added a feature NETIF_F_SKB_NO_LINEAR to identify whether th= e >> >> Does it make sense to use ETHTOOL_TX_COPYBREAK tunable in ethtool to >> configure if the data is copied or not? > > As far as I can grep, only mlx4 supports this, and it has a different > meaning in that driver. > So I guess a new netdev_feature would be a better solution. > >>> 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(-) >>>=20 >>> 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 *vd= ev) >>> =09/* Set up network device as normal. */ >>> =09dev->priv_flags |=3D IFF_UNICAST_FLT | IFF_LIVE_ADDR_CHANGE; >>> =09dev->netdev_ops =3D &virtnet_netdev; >>> -=09dev->features =3D NETIF_F_HIGHDMA; >>> +=09dev->features =3D NETIF_F_HIGHDMA | NETIF_F_SKB_NO_LINEAR; >>> =20 >>> =09dev->ethtool_ops =3D &virtnet_ethtool_ops; >>> =09SET_NETDEV_DEV(dev, &vdev->dev); >>> diff --git a/include/linux/netdev_features.h b/include/linux/netdev_fea= tures.h >>> index 934de56..8dd28e2 100644 >>> --- a/include/linux/netdev_features.h >>> +++ b/include/linux/netdev_features.h >>> @@ -85,9 +85,11 @@ enum { >>> =20 >>> =09NETIF_F_HW_MACSEC_BIT,=09=09/* Offload MACsec operations */ >>> =20 >>> +=09NETIF_F_SKB_NO_LINEAR_BIT,=09/* Allow skb linear is empty */ >>> + >>> =09/* >>> =09 * Add your fresh new feature above and remember to update >>> -=09 * netdev_features_strings[] in net/core/ethtool.c and maybe >>> +=09 * netdev_features_strings[] in net/ethtool/common.c and maybe >>> =09 * some feature mask #defines below. Please also describe it >>> =09 * in Documentation/networking/netdev-features.rst. >>> =09 */ >>> @@ -157,6 +159,7 @@ enum { >>> #define NETIF_F_GRO_FRAGLIST=09__NETIF_F(GRO_FRAGLIST) >>> #define NETIF_F_GSO_FRAGLIST=09__NETIF_F(GSO_FRAGLIST) >>> #define NETIF_F_HW_MACSEC=09__NETIF_F(HW_MACSEC) >>> +#define NETIF_F_SKB_NO_LINEAR=09__NETIF_F(SKB_NO_LINEAR) >>> =20 >>> /* Finds the next feature with the highest number of the range of star= t 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 @@ >>> =09[NETIF_F_HW_TLS_RX_BIT] =3D=09 "tls-hw-rx-offload", >>> =09[NETIF_F_GRO_FRAGLIST_BIT] =3D=09 "rx-gro-list", >>> =09[NETIF_F_HW_MACSEC_BIT] =3D=09 "macsec-hw-offload", >>> +=09[NETIF_F_SKB_NO_LINEAR_BIT] =3D=09 "skb-no-linear", > > I completely forgot to add that you'd better to mention in both > enumeration/feature and its Ethtool string that the feature applies > to Tx path. > Smth like: > > NETIF_F_SKB_TX_NO_LINEAR{,_BIT}, "skb-tx-no-linear" > or > NETIF_F_TX_SKB_NO_LINEAR{,_BIT}, "tx-skb-no-linear" > > Otherwise, it may be confusing for users and developers. OR, I think we may tight the feature with the new approach to build skbs by page as it makes no sense for anything else. So, if we define something like: NETIF_F_XSK_TX_GENERIC_ZC{,_BIT}, "xsk-tx-generic-zerocopy", then user can toggle your new XSK Tx path on/off via Ethtool for drivers that will support it (don't forget to add it to hw_features for virtio_net then). >>> }; >>> =20 >>> 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) >>> =09sock_wfree(skb); >>> } >>> =20 >>> +static struct sk_buff *xsk_build_skb_zerocopy(struct xdp_sock *xs, >>> +=09=09=09=09=09 struct xdp_desc *desc) >>> +{ >>> +=09u32 len, offset, copy, copied; >>> +=09struct sk_buff *skb; >>> +=09struct page *page; >>> +=09char *buffer; >>> +=09int err, i; >>> +=09u64 addr; >>> + >>> +=09skb =3D sock_alloc_send_skb(&xs->sk, 0, 1, &err); >>> +=09if (unlikely(!skb)) >>> +=09=09return NULL; >>> + >>> +=09addr =3D desc->addr; >>> +=09len =3D desc->len; >>> + >>> +=09buffer =3D xsk_buff_raw_get_data(xs->pool, addr); >>> +=09offset =3D offset_in_page(buffer); >>> +=09addr =3D buffer - (char *)xs->pool->addrs; >>> + >>> +=09for (copied =3D 0, i =3D 0; copied < len; ++i) { >>> +=09=09page =3D xs->pool->umem->pgs[addr >> PAGE_SHIFT]; >>> + >>> +=09=09get_page(page); >>> + >>> +=09=09copy =3D min((u32)(PAGE_SIZE - offset), len - copied); >>> + >>> +=09=09skb_fill_page_desc(skb, i, page, offset, copy); >>> + >>> +=09=09copied +=3D copy; >>> +=09=09addr +=3D copy; >>> +=09=09offset =3D 0; >>> +=09} >>> + >>> +=09skb->len +=3D len; >>> +=09skb->data_len +=3D len; >>> +=09skb->truesize +=3D len; >>> + >>> +=09refcount_add(len, &xs->sk.sk_wmem_alloc); >>> + >>> +=09return skb; >>> +} >>> + >>> +static struct sk_buff *xsk_build_skb(struct xdp_sock *xs, >>> +=09=09=09=09 struct xdp_desc *desc, int *err) >>> +{ >>> +=09struct sk_buff *skb; >>> + >>> +=09if (xs->dev->features & NETIF_F_SKB_NO_LINEAR) { >>> +=09=09skb =3D xsk_build_skb_zerocopy(xs, desc); >>> +=09=09if (unlikely(!skb)) { >>> +=09=09=09*err =3D -ENOMEM; >>> +=09=09=09return NULL; >>> +=09=09} >>> +=09} else { >>> +=09=09char *buffer; >>> +=09=09u64 addr; >>> +=09=09u32 len; >>> +=09=09int err; >>> + >>> +=09=09len =3D desc->len; >>> +=09=09skb =3D sock_alloc_send_skb(&xs->sk, len, 1, &err); >>> +=09=09if (unlikely(!skb)) { >>> +=09=09=09*err =3D -ENOMEM; >>> +=09=09=09return NULL; >>> +=09=09} >>> + >>> +=09=09skb_put(skb, len); >>> +=09=09addr =3D desc->addr; >>> +=09=09buffer =3D xsk_buff_raw_get_data(xs->pool, desc->addr); >>> +=09=09err =3D skb_store_bits(skb, 0, buffer, len); >>> + >>> +=09=09if (unlikely(err)) { >>> +=09=09=09kfree_skb(skb); >>> +=09=09=09*err =3D -EINVAL; >>> +=09=09=09return NULL; >>> +=09=09} >>> +=09} >>> + >>> +=09skb->dev =3D xs->dev; >>> +=09skb->priority =3D xs->sk.sk_priority; >>> +=09skb->mark =3D xs->sk.sk_mark; >>> +=09skb_shinfo(skb)->destructor_arg =3D (void *)(long)desc->addr; >>> +=09skb->destructor =3D xsk_destruct_skb; >>> + >>> +=09return skb; >>> +} >>> + >>> static int xsk_generic_xmit(struct sock *sk) >>> { >>> =09struct xdp_sock *xs =3D xdp_sk(sk); >>> @@ -446,43 +535,28 @@ static int xsk_generic_xmit(struct sock *sk) >>> =09=09goto out; >>> =20 >>> =09while (xskq_cons_peek_desc(xs->tx, &desc, xs->pool)) { >>> -=09=09char *buffer; >>> -=09=09u64 addr; >>> -=09=09u32 len; >>> - >>> =09=09if (max_batch-- =3D=3D 0) { >>> =09=09=09err =3D -EAGAIN; >>> =09=09=09goto out; >>> =09=09} >>> =20 >>> -=09=09len =3D desc.len; >>> -=09=09skb =3D sock_alloc_send_skb(sk, len, 1, &err); >>> +=09=09skb =3D xsk_build_skb(xs, &desc, &err); >>> =09=09if (unlikely(!skb)) >>> =09=09=09goto out; >>> =20 >>> -=09=09skb_put(skb, len); >>> -=09=09addr =3D desc.addr; >>> -=09=09buffer =3D xsk_buff_raw_get_data(xs->pool, addr); >>> -=09=09err =3D skb_store_bits(skb, 0, buffer, len); >>> =09=09/* This is the backpressure mechanism for the Tx path. >>> =09=09 * Reserve space in the completion queue and only proceed >>> =09=09 * if there is space in it. This avoids having to implement >>> =09=09 * any buffering in the Tx path. >>> =09=09 */ >>> =09=09spin_lock_irqsave(&xs->pool->cq_lock, flags); >>> -=09=09if (unlikely(err) || xskq_prod_reserve(xs->pool->cq)) { >>> +=09=09if (xskq_prod_reserve(xs->pool->cq)) { >>> =09=09=09spin_unlock_irqrestore(&xs->pool->cq_lock, flags); >>> =09=09=09kfree_skb(skb); >>> =09=09=09goto out; >>> =09=09} >>> =09=09spin_unlock_irqrestore(&xs->pool->cq_lock, flags); >>> =20 >>> -=09=09skb->dev =3D xs->dev; >>> -=09=09skb->priority =3D sk->sk_priority; >>> -=09=09skb->mark =3D sk->sk_mark; >>> -=09=09skb_shinfo(skb)->destructor_arg =3D (void *)(long)desc.addr; >>> -=09=09skb->destructor =3D xsk_destruct_skb; >>> - >>> =09=09err =3D __dev_direct_xmit(skb, xs->queue_id); >>> =09=09if (err =3D=3D NETDEV_TX_BUSY) { >>> =09=09=09/* Tell user-space to retry the send */ >>>=20 > > Al Al