From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tushar Dave Subject: Re: [RFC PATCH 00/24] Introducing AF_XDP support Date: Mon, 26 Mar 2018 15:54:18 -0700 Message-ID: References: <20180131135356.19134-1-bjorn.topel@gmail.com> <20180326183810.2ef4e29f@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Cc: =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= , magnus.karlsson@intel.com, Alexander Duyck , Alexander Duyck , John Fastabend , Alexei Starovoitov , willemdebruijn.kernel@gmail.com, Daniel Borkmann , Linux Kernel Network Developers , =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= , michael.lundkvist@ericsson.com, jesse.brandeburg@intel.com, anjali.singhai@intel.com, jeffrey.b.shaw@intel.com, ferruh.yigit@intel.com, qi.z.zhang@intel.com To: Jesper Dangaard Brouer , William Tu Return-path: Received: from userp2130.oracle.com ([156.151.31.86]:40418 "EHLO userp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751739AbeCZWyw (ORCPT ); Mon, 26 Mar 2018 18:54:52 -0400 In-Reply-To: <20180326183810.2ef4e29f@redhat.com> Content-Language: en-US Sender: netdev-owner@vger.kernel.org List-ID: On 03/26/2018 09:38 AM, Jesper Dangaard Brouer wrote: > > On Mon, 26 Mar 2018 09:06:54 -0700 William Tu wrote: > >> On Wed, Jan 31, 2018 at 5:53 AM, Björn Töpel wrote: >>> From: Björn Töpel >>> >>> This RFC introduces a new address family called AF_XDP that is >>> optimized for high performance packet processing and zero-copy >>> semantics. Throughput improvements can be up to 20x compared to V2 and >>> V3 for the micro benchmarks included. Would be great to get your >>> feedback on it. Note that this is the follow up RFC to AF_PACKET V4 >>> from November last year. The feedback from that RFC submission and the >>> presentation at NetdevConf in Seoul was to create a new address family >>> instead of building on top of AF_PACKET. AF_XDP is this new address >>> family. >>> >>> The main difference between AF_XDP and AF_PACKET V2/V3 on a descriptor >>> level is that TX and RX descriptors are separated from packet >>> buffers. An RX or TX descriptor points to a data buffer in a packet >>> buffer area. RX and TX can share the same packet buffer so that a >>> packet does not have to be copied between RX and TX. Moreover, if a >>> packet needs to be kept for a while due to a possible retransmit, then >>> the descriptor that points to that packet buffer can be changed to >>> point to another buffer and reused right away. This again avoids >>> copying data. >>> >>> The RX and TX descriptor rings are registered with the setsockopts >>> XDP_RX_RING and XDP_TX_RING, similar to AF_PACKET. The packet buffer >>> area is allocated by user space and registered with the kernel using >>> the new XDP_MEM_REG setsockopt. All these three areas are shared >>> between user space and kernel space. The socket is then bound with a >>> bind() call to a device and a specific queue id on that device, and it >>> is not until bind is completed that traffic starts to flow. >>> >>> An XDP program can be loaded to direct part of the traffic on that >>> device and queue id to user space through a new redirect action in an >>> XDP program called bpf_xdpsk_redirect that redirects a packet up to >>> the socket in user space. All the other XDP actions work just as >>> before. Note that the current RFC requires the user to load an XDP >>> program to get any traffic to user space (for example all traffic to >>> user space with the one-liner program "return >>> bpf_xdpsk_redirect();"). We plan on introducing a patch that removes >>> this requirement and sends all traffic from a queue to user space if >>> an AF_XDP socket is bound to it. >>> >>> AF_XDP can operate in three different modes: XDP_SKB, XDP_DRV, and >>> XDP_DRV_ZC (shorthand for XDP_DRV with a zero-copy allocator as there >>> is no specific mode called XDP_DRV_ZC). If the driver does not have >>> support for XDP, or XDP_SKB is explicitly chosen when loading the XDP >>> program, XDP_SKB mode is employed that uses SKBs together with the >>> generic XDP support and copies out the data to user space. A fallback >>> mode that works for any network device. On the other hand, if the >>> driver has support for XDP (all three NDOs: ndo_bpf, ndo_xdp_xmit and >>> ndo_xdp_flush), these NDOs, without any modifications, will be used by >>> the AF_XDP code to provide better performance, but there is still a >>> copy of the data into user space. The last mode, XDP_DRV_ZC, is XDP >>> driver support with the zero-copy user space allocator that provides >>> even better performance. In this mode, the networking HW (or SW driver >>> if it is a virtual driver like veth) DMAs/puts packets straight into >>> the packet buffer that is shared between user space and kernel >>> space. The RX and TX descriptor queues of the networking HW are NOT >>> shared to user space. Only the kernel can read and write these and it >>> is the kernel driver's responsibility to translate these HW specific >>> descriptors to the HW agnostic ones in the virtual descriptor rings >>> that user space sees. This way, a malicious user space program cannot >>> mess with the networking HW. This mode though requires some extensions >>> to XDP. >>> >>> To get the XDP_DRV_ZC mode to work for RX, we chose to introduce a >>> buffer pool concept so that the same XDP driver code can be used for >>> buffers allocated using the page allocator (XDP_DRV), the user-space >>> zero-copy allocator (XDP_DRV_ZC), or some internal driver specific >>> allocator/cache/recycling mechanism. The ndo_bpf call has also been >>> extended with two commands for registering and unregistering an XSK >>> socket and is in the RX case mainly used to communicate some >>> information about the user-space buffer pool to the driver. >>> >>> For the TX path, our plan was to use ndo_xdp_xmit and ndo_xdp_flush, >>> but we run into problems with this (further discussion in the >>> challenges section) and had to introduce a new NDO called >>> ndo_xdp_xmit_xsk (xsk = XDP socket). It takes a pointer to a netdevice >>> and an explicit queue id that packets should be sent out on. In >>> contrast to ndo_xdp_xmit, it is asynchronous and pulls packets to be >>> sent from the xdp socket (associated with the dev and queue >>> combination that was provided with the NDO call) using a callback >>> (get_tx_packet), and when they have been transmitted it uses another >>> callback (tx_completion) to signal completion of packets. These >>> callbacks are set via ndo_bpf in the new XDP_REGISTER_XSK >>> command. ndo_xdp_xmit_xsk is exclusively used by the XDP socket code >>> and thus does not clash with the XDP_REDIRECT use of >>> ndo_xdp_xmit. This is one of the reasons that the XDP_DRV mode >>> (without ZC) is currently not supported by TX. Please have a look at >>> the challenges section for further discussions. >>> >>> The AF_XDP bind call acts on a queue pair (channel in ethtool speak), >>> so the user needs to steer the traffic to the zero-copy enabled queue >>> pair. Which queue to use, is up to the user. >>> >>> For an untrusted application, HW packet steering to a specific queue >>> pair (the one associated with the application) is a requirement, as >>> the application would otherwise be able to see other user space >>> processes' packets. If the HW cannot support the required packet >>> steering, XDP_DRV or XDP_SKB mode have to be used as they do not >>> expose the NIC's packet buffer into user space as the packets are >>> copied into user space from the NIC's packet buffer in the kernel. >>> >>> There is a xdpsock benchmarking/test application included. Say that >>> you would like your UDP traffic from port 4242 to end up in queue 16, >>> that we will enable AF_XDP on. Here, we use ethtool for this: >>> >>> ethtool -N p3p2 rx-flow-hash udp4 fn >>> ethtool -N p3p2 flow-type udp4 src-port 4242 dst-port 4242 \ >>> action 16 >>> >>> Running the l2fwd benchmark in XDP_DRV_ZC mode can then be done using: >>> >>> samples/bpf/xdpsock -i p3p2 -q 16 -l -N >>> >>> For XDP_SKB mode, use the switch "-S" instead of "-N" and all options >>> can be displayed with "-h", as usual. >>> >>> We have run some benchmarks on a dual socket system with two Broadwell >>> E5 2660 @ 2.0 GHz with hyperthreading turned off. Each socket has 14 >>> cores which gives a total of 28, but only two cores are used in these >>> experiments. One for TR/RX and one for the user space application. The >>> memory is DDR4 @ 2133 MT/s (1067 MHz) and the size of each DIMM is >>> 8192MB and with 8 of those DIMMs in the system we have 64 GB of total >>> memory. The compiler used is gcc version 5.4.0 20160609. The NIC is an >>> Intel I40E 40Gbit/s using the i40e driver. >>> >>> Below are the results in Mpps of the I40E NIC benchmark runs for 64 >>> byte packets, generated by commercial packet generator HW that is >>> generating packets at full 40 Gbit/s line rate. >>> >>> XDP baseline numbers without this RFC: >>> xdp_rxq_info --action XDP_DROP 31.3 Mpps >>> xdp_rxq_info --action XDP_TX 16.7 Mpps >>> >>> XDP performance with this RFC i.e. with the buffer allocator: >>> XDP_DROP 21.0 Mpps >>> XDP_TX 11.9 Mpps >>> >>> AF_PACKET V4 performance from previous RFC on 4.14-rc7: >>> Benchmark V2 V3 V4 V4+ZC >>> rxdrop 0.67 0.73 0.74 33.7 >>> txpush 0.98 0.98 0.91 19.6 >>> l2fwd 0.66 0.71 0.67 15.5 >>> >>> AF_XDP performance: >>> Benchmark XDP_SKB XDP_DRV XDP_DRV_ZC (all in Mpps) >>> rxdrop 3.3 11.6 16.9 >>> txpush 2.2 NA* 21.8 >>> l2fwd 1.7 NA* 10.4 >>> >> >> Hi, >> I also did an evaluation of AF_XDP, however the performance isn't as >> good as above. >> I'd like to share the result and see if there are some tuning suggestions. >> >> System: >> 16 core, Intel(R) Xeon(R) CPU E5-2440 v2 @ 1.90GHz >> Intel 10G X540-AT2 ---> so I can only run XDP_SKB mode > > Hmmm, why is X540-AT2 not able to use XDP natively? > >> AF_XDP performance: >> Benchmark XDP_SKB >> rxdrop 1.27 Mpps >> txpush 0.99 Mpps >> l2fwd 0.85 Mpps > > Definitely too low... > > What is the performance if you drop packets via iptables? > > Command: > $ iptables -t raw -I PREROUTING -p udp --dport 9 --j DROP > >> NIC configuration: >> the command >> "ethtool -N p3p2 flow-type udp4 src-port 4242 dst-port 4242 action 16" >> doesn't work on my ixgbe driver, so I use ntuple: >> >> ethtool -K enp10s0f0 ntuple on >> ethtool -U enp10s0f0 flow-type udp4 src-ip 10.1.1.100 action 1 >> then >> echo 1 > /proc/sys/net/core/bpf_jit_enable >> ./xdpsock -i enp10s0f0 -r -S --queue=1 >> >> I also take a look at perf result: >> For rxdrop: >> 86.56% xdpsock xdpsock [.] main >> 9.22% xdpsock [kernel.vmlinux] [k] nmi >> 4.23% xdpsock xdpsock [.] xq_enq > > It looks very strange that you see non-maskable interrupt's (NMI) being > this high... > > >> For l2fwd: >> 20.81% xdpsock xdpsock [.] main >> 10.64% xdpsock [kernel.vmlinux] [k] clflush_cache_range > > Oh, clflush_cache_range is being called! > Do your system use an IOMMU ? Whats the implication here. Should IOMMU be disabled? I'm asking because I do see a huge difference while running pktgen test for my performance benchmarks, with and without intel_iommu. -Tushar > >> 8.46% xdpsock [kernel.vmlinux] [k] xsk_sendmsg >> 6.72% xdpsock [kernel.vmlinux] [k] skb_set_owner_w >> 5.89% xdpsock [kernel.vmlinux] [k] __domain_mapping >> 5.74% xdpsock [kernel.vmlinux] [k] alloc_skb_with_frags >> 4.62% xdpsock [kernel.vmlinux] [k] netif_skb_features >> 3.96% xdpsock [kernel.vmlinux] [k] ___slab_alloc >> 3.18% xdpsock [kernel.vmlinux] [k] nmi > > Again high count for NMI ?!? > > Maybe you just forgot to tell perf that you want it to decode the > bpf_prog correctly? > > https://prototype-kernel.readthedocs.io/en/latest/bpf/troubleshooting.html#perf-tool-symbols > > Enable via: > $ sysctl net/core/bpf_jit_kallsyms=1 > > And use perf report (while BPF is STILL LOADED): > > $ perf report --kallsyms=/proc/kallsyms > > E.g. for emailing this you can use this command: > > $ perf report --sort cpu,comm,dso,symbol --kallsyms=/proc/kallsyms --no-children --stdio -g none | head -n 40 > > >> I observed that the i40e's XDP_SKB result is much better than my ixgbe's result. >> I wonder in XDP_SKB mode, does the driver make performance difference? >> Or my cpu (E5-2440 v2 @ 1.90GHz) is too old? > > I suspect some setup issue on your system. >