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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 35523C433DB for ; Mon, 18 Jan 2021 13:02:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E91DE22571 for ; Mon, 18 Jan 2021 13:02:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726685AbhARNCM (ORCPT ); Mon, 18 Jan 2021 08:02:12 -0500 Received: from mail-40136.protonmail.ch ([185.70.40.136]:56964 "EHLO mail-40136.protonmail.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391981AbhARNBG (ORCPT ); Mon, 18 Jan 2021 08:01:06 -0500 Date: Mon, 18 Jan 2021 13:00:17 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=pm.me; s=protonmail; t=1610974820; bh=/NaeKoU4Q/v51eOBH7d6BpzM6okVuiuPHOFagTI+ZbM=; h=Date:To:From:Cc:Reply-To:Subject:In-Reply-To:References:From; b=O4X6YWp+K5tAMwBPR1h6loJZm9y13TAg7xcV7N8Vd2DsUb9x3U4rBGvo5/sahYnV6 mk9Ob7BlYhVrrOGYJK2h6mEfW5vxUR48x6HlrTFWWC4olxd32uGXUYYIIMSYgEO0r9 uK1GuQG9gNc97EHtfMumy6C03omSaFo+D3KaG066lfJJBDWqcI3DzzKAhfKjn3BAa/ 6Lc55u2bfo0SA2YrKT6wzBco3/D61SZ5jPATP+AV2ez1pxLWlgeXVnPa4KGr6xOuKc WikyAXBfjLrTb/qhqRRR13yK0IF1Z9HxG0Iuyh5SL3fS1UhaO4jfEIEQ5VyDAgB7pc IVrPWVx9aUocg== 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: <20210118125937.4088-1-alobakin@pm.me> In-Reply-To: <4a4b475b-0e79-6cf6-44f5-44d45b5d85b5@huawei.com> References: <579fa463bba42ac71591540a1811dca41d725350.1610764948.git.xuanzhuo@linux.alibaba.com> <4a4b475b-0e79-6cf6-44f5-44d45b5d85b5@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org 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 0x1d= bb, 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? 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 *vde= v) >> =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_feat= ures.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 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 @@ >> =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. >> }; >> =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