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[23.128.96.18]) by mx.google.com with ESMTP id b2si7126196ejc.551.2021.01.18.07.22.39; Mon, 18 Jan 2021 07:23:03 -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=@gmail.com header.s=20161025 header.b=ntGWnX3S; 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=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2405429AbhARPTx (ORCPT + 99 others); Mon, 18 Jan 2021 10:19:53 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34736 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2405459AbhARPLd (ORCPT ); Mon, 18 Jan 2021 10:11:33 -0500 Received: from mail-pl1-x62c.google.com (mail-pl1-x62c.google.com [IPv6:2607:f8b0:4864:20::62c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1C12AC061574; Mon, 18 Jan 2021 07:10:52 -0800 (PST) Received: by mail-pl1-x62c.google.com with SMTP id x12so8784793plr.10; Mon, 18 Jan 2021 07:10:52 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=CZkRE6yPZNd5+6Zz0cmjQz4RUMR00hABFphuo4zVslE=; b=ntGWnX3SI3AZMTMF/CZSkC9qspmvVU8LZRDqh7XIkXviWWKL5NwmaImWhROvMci1qF BbRF7WZPn/TMtBnm87lBZpyd+Q7rmIWc/RhfWjvcmelCpwf5XfZsAayCLfTVr3SNvFgC svfOnUT7OQvE+O43XB2kZoHsFxygNgYU5YZCoyOJJ3t4iSkXPEaUzC1ZVejR0vSuJk4p yR3IXxr00LhvdF4aLcibDPWr6PkWim5uHFLtiaKuwZH6n1CLLzwkmpSg53RSuU6tVipj pgJL0ihu9usf6YTj2uOlXOY6s4cVSPPTRIC4bZ22TAGdcMAHRPDSW+yO9WD0LzEITVqY m/jQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=CZkRE6yPZNd5+6Zz0cmjQz4RUMR00hABFphuo4zVslE=; b=bP5LbXfRkHZgvw/htdj5f95UKUWBeaYPcvwPMXuZj8xdZ0rQ6XGDowCqBCvC5h1QOZ w35SiLSQf2cuhCUqqn2JDrFjxke68t4Z+sA72Sg5KJTiWPCPUTdrDz4wwcrhpOMXON5P CFcUaU4tZMc8u8Mqw7w5rK3pmls5k7yP+Wq971tEJAvvAx7oDtrksLENhbzm/06ik2G3 lfKqmQy4hnJhtKBpP5a1837Op/c2Oea+9AEjHT+XEMghpCIPjJIjcqn7Bxla3P1UkSoa DZJsXDLz/z3fGCfmRyAs4krlmtoFTsty7uj3xUi2OtiEzRgT9AKhCupnnVVkl1u773eI Rr2A== X-Gm-Message-State: AOAM533Mu3AEpOnN9Lma6vAoFOKuiWd3dyeKdkGLlXAd99vj5ijm10tD rZMOTYJ50QoF3oTUdPJf8Q9FPltJYJi7VF+8N7M= X-Received: by 2002:a17:90a:4a85:: with SMTP id f5mr27137593pjh.117.1610982651539; Mon, 18 Jan 2021 07:10:51 -0800 (PST) MIME-Version: 1.0 References: <579fa463bba42ac71591540a1811dca41d725350.1610764948.git.xuanzhuo@linux.alibaba.com> <4a4b475b-0e79-6cf6-44f5-44d45b5d85b5@huawei.com> <20210118125937.4088-1-alobakin@pm.me> <20210118143948.8706-1-alobakin@pm.me> In-Reply-To: <20210118143948.8706-1-alobakin@pm.me> From: Magnus Karlsson Date: Mon, 18 Jan 2021 16:10:40 +0100 Message-ID: Subject: Re: [PATCH bpf-next] xsk: build skb by page To: Alexander Lobakin Cc: Yunsheng Lin , Xuan Zhuo , "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 , Miaohe Lin , Mauro Carvalho Chehab , Antoine Tenart , Michal Kubecek , Andrew Lunn , Florian Fainelli , Meir Lichtinger , virtualization@lists.linux-foundation.org, bpf , Network Development , open list Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 18, 2021 at 3:47 PM Alexander Lobakin wrote: > > 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 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? > > > > 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(-) > >>> > >>> 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", > > > > 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. I prefer one of these names for the property as they clearly describe a feature that the driver supports. > 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", This one I misunderstood first. I thought: "this is not zerocopy", but you are right it is. It is zero-copy implemented with skb:s. But in my mind, the NO_LINEAR version that you suggested are clearer. > 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). > > >>> }; > >>> > >>> 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 */ > >>> > > > > Al > > Al >