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[79.177.39.148]) by smtp.gmail.com with ESMTPSA id d2sm29288739wre.39.2021.01.18.03.57.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 18 Jan 2021 03:57:46 -0800 (PST) Date: Mon, 18 Jan 2021 06:57:41 -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 , Willem de Bruijn , Steffen Klassert , Alexander Lobakin , Miaohe Lin , Mauro Carvalho Chehab , Antoine Tenart , Michal Kubecek , Andrew Lunn , Florian Fainelli , Meir Lichtinger , virtualization@lists.linux-foundation.org, bpf@vger.kernel.org Subject: Re: [PATCH bpf-next] xsk: build skb by page Message-ID: <20210118065333-mutt-send-email-mst@kernel.org> References: <579fa463bba42ac71591540a1811dca41d725350.1610764948.git.xuanzhuo@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <579fa463bba42ac71591540a1811dca41d725350.1610764948.git.xuanzhuo@linux.alibaba.com> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Sat, Jan 16, 2021 at 10:44:53AM +0800, 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 > 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% Nice, but it looks like the patch presented wouldn't compile. It's worth retesting after you actually make it compile. > 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) Rather than passing int *err, you can return PTR_ERR. Seems cleaner ... > +{ > + 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; So err is int here > + > + len = desc->len; > + skb = sock_alloc_send_skb(&xs->sk, len, 1, &err); > + if (unlikely(!skb)) { > + *err = -ENOMEM; .. and you dereference it here > + 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; Same thing here ... how does it compile? > + 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 */ > -- > 1.8.3.1