| Message ID | 20230719132421.584801-1-maciej.fijalkowski@intel.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | xsk: multi-buffer support | expand |
Hello: This series was applied to bpf/bpf-next.git (master) by Alexei Starovoitov <ast@kernel.org>: On Wed, 19 Jul 2023 15:23:57 +0200 you wrote: > v6->v7: > - rebase...[Alexei] > > v5->v6: > - update bpf_xdp_query_opts__last_field in patch 10 [Alexei] > > v4->v5: > - align options argument size to match options from xdp_desc [Benjamin] > - cleanup skb from xdp_sock on socket termination [Toke] > - introduce new netlink attribute for letting user space know about Tx > frag limit; this substitutes xdp_features flag previously dedicated > for setting ZC multi-buffer support [Toke, Jakub] > - include i40e ZC multi-buffer support > - enable TOO_MANY_FRAGS for ZC on xskxceiver; this is now possible due > to netlink attribute mentioned two bullets above > > [...] Here is the summary with links: - [v7,bpf-next,01/24] xsk: prepare 'options' in xdp_desc for multi-buffer use https://git.kernel.org/bpf/bpf-next/c/63a64a56bc3f - [v7,bpf-next,02/24] xsk: introduce XSK_USE_SG bind flag for xsk socket https://git.kernel.org/bpf/bpf-next/c/81470b5c3c66 - [v7,bpf-next,03/24] xsk: prepare both copy and zero-copy modes to co-exist https://git.kernel.org/bpf/bpf-next/c/556444c4e683 - [v7,bpf-next,04/24] xsk: move xdp_buff's data length check to xsk_rcv_check https://git.kernel.org/bpf/bpf-next/c/faa91b839b09 - [v7,bpf-next,05/24] xsk: add support for AF_XDP multi-buffer on Rx path https://git.kernel.org/bpf/bpf-next/c/804627751b42 - [v7,bpf-next,06/24] xsk: introduce wrappers and helpers for supporting multi-buffer in Tx path https://git.kernel.org/bpf/bpf-next/c/b7f72a30e9ac - [v7,bpf-next,07/24] xsk: allow core/drivers to test EOP bit https://git.kernel.org/bpf/bpf-next/c/1b725b0c8163 - [v7,bpf-next,08/24] xsk: add support for AF_XDP multi-buffer on Tx path https://git.kernel.org/bpf/bpf-next/c/cf24f5a5feea - [v7,bpf-next,09/24] xsk: discard zero length descriptors in Tx path https://git.kernel.org/bpf/bpf-next/c/07428da9e25a - [v7,bpf-next,10/24] xsk: add new netlink attribute dedicated for ZC max frags https://git.kernel.org/bpf/bpf-next/c/13ce2daa259a - [v7,bpf-next,11/24] xsk: support mbuf on ZC RX https://git.kernel.org/bpf/bpf-next/c/24ea50127ecf - [v7,bpf-next,12/24] ice: xsk: add RX multi-buffer support https://git.kernel.org/bpf/bpf-next/c/1bbc04de607b - [v7,bpf-next,13/24] i40e: xsk: add RX multi-buffer support https://git.kernel.org/bpf/bpf-next/c/1c9ba9c14658 - [v7,bpf-next,14/24] xsk: support ZC Tx multi-buffer in batch API https://git.kernel.org/bpf/bpf-next/c/d5581966040f - [v7,bpf-next,15/24] ice: xsk: Tx multi-buffer support https://git.kernel.org/bpf/bpf-next/c/eeb2b5381038 - [v7,bpf-next,16/24] i40e: xsk: add TX multi-buffer support https://git.kernel.org/bpf/bpf-next/c/a92b96c4ae10 - [v7,bpf-next,17/24] xsk: add multi-buffer documentation https://git.kernel.org/bpf/bpf-next/c/49ca37d0d825 - [v7,bpf-next,18/24] selftests/xsk: transmit and receive multi-buffer packets https://git.kernel.org/bpf/bpf-next/c/17f1034dd76d - [v7,bpf-next,19/24] selftests/xsk: add basic multi-buffer test https://git.kernel.org/bpf/bpf-next/c/f540d44e05cf - [v7,bpf-next,20/24] selftests/xsk: add unaligned mode test for multi-buffer https://git.kernel.org/bpf/bpf-next/c/1005a226da9a - [v7,bpf-next,21/24] selftests/xsk: add invalid descriptor test for multi-buffer https://git.kernel.org/bpf/bpf-next/c/697604492b64 - [v7,bpf-next,22/24] selftests/xsk: add metadata copy test for multi-buff https://git.kernel.org/bpf/bpf-next/c/f80ddbec4762 - [v7,bpf-next,23/24] selftests/xsk: add test for too many frags https://git.kernel.org/bpf/bpf-next/c/807bf4da2049 - [v7,bpf-next,24/24] selftests/xsk: reset NIC settings to default after running test suite https://git.kernel.org/bpf/bpf-next/c/3666bccab43a You are awesome, thank you!
v6->v7: - rebase...[Alexei] v5->v6: - update bpf_xdp_query_opts__last_field in patch 10 [Alexei] v4->v5: - align options argument size to match options from xdp_desc [Benjamin] - cleanup skb from xdp_sock on socket termination [Toke] - introduce new netlink attribute for letting user space know about Tx frag limit; this substitutes xdp_features flag previously dedicated for setting ZC multi-buffer support [Toke, Jakub] - include i40e ZC multi-buffer support - enable TOO_MANY_FRAGS for ZC on xskxceiver; this is now possible due to netlink attribute mentioned two bullets above v3->v4: -rely on ynl for adding new xdp_features flag [Jakub] - move xskb_list to xsk_buff_pool v2->v3: - Fix issue with the next valid packet getting dropped after an invalid packet with MAX_SKB_FRAGS + 1 frags [Magnus] - query NETDEV_XDP_ACT_ZC_SG flag within xskxceiver and act on it - remove redundant include in xsk.c [kernel test robot] - s/NETDEV_XDP_ACT_NDO_ZC_SG/NETDEV_XDP_ACT_ZC_SG + kernel doc [Magnus, Simon] v1->v2: - fix spelling issues in commit messages [Simon] - remove XSK_DESC_MAX_FRAGS, use MAX_SKB_FRAGS instead [Stan, Alexei] - add documentation patch - fix build error from kernel test robot on patch 10 This series of patches add multi-buffer support for AF_XDP. XDP and various NIC drivers already have support for multi-buffer packets. With this patch set, programs using AF_XDP sockets can now also receive and transmit multi-buffer packets both in copy as well as zero-copy mode. ZC multi-buffer implementation is based on ice driver. Some definitions to put us all on the same page: * A packet consists of one or more frames * A descriptor in one of the AF_XDP rings always refers to a single frame. In the case the packet consists of a single frame, the descriptor refers to the whole packet. To represent a packet consisting of multiple frames, we introduce a new flag called XDP_PKT_CONTD in the options field of the Rx and Tx descriptors. If it is true (1) the packet continues with the next descriptor and if it is false (0) it means this is the last descriptor of the packet. Why the reverse logic of end-of-packet (eop) flag found in many NICs? Just to preserve compatibility with non-multi-buffer applications that have this bit set to false for all packets on Rx, and the apps set the options field to zero for Tx, as anything else will be treated as an invalid descriptor. These are the semantics for producing packets onto XSK Tx ring consisting of multiple frames: * When an invalid descriptor is found, all the other descriptors/frames of this packet are marked as invalid and not completed. The next descriptor is treated as the start of a new packet, even if this was not the intent (because we cannot guess the intent). As before, if your program is producing invalid descriptors you have a bug that must be fixed. * Zero length descriptors are treated as invalid descriptors. * For copy mode, the maximum supported number of frames in a packet is equal to CONFIG_MAX_SKB_FRAGS + 1. If it is exceeded, all descriptors accumulated so far are dropped and treated as invalid. To produce an application that will work on any system regardless of this config setting, limit the number of frags to 18, as the minimum value of the config is 17. * For zero-copy mode, the limit is up to what the NIC HW supports. User space can discover this via newly introduced NETDEV_A_DEV_XDP_ZC_MAX_SEGS netlink attribute. Here is an example Tx path pseudo-code (using libxdp interfaces for simplicity) ignoring that the umem is finite in size, and that we eventually will run out of packets to send. Also assumes pkts.addr points to a valid location in the umem. void tx_packets(struct xsk_socket_info *xsk, struct pkt *pkts, int batch_size) { u32 idx, i, pkt_nb = 0; xsk_ring_prod__reserve(&xsk->tx, batch_size, &idx); for (i = 0; i < batch_size;) { u64 addr = pkts[pkt_nb].addr; u32 len = pkts[pkt_nb].size; do { struct xdp_desc *tx_desc; tx_desc = xsk_ring_prod__tx_desc(&xsk->tx, idx + i++); tx_desc->addr = addr; if (len > xsk_frame_size) { tx_desc->len = xsk_frame_size; tx_desc->options |= XDP_PKT_CONTD; } else { tx_desc->len = len; tx_desc->options = 0; pkt_nb++; } len -= tx_desc->len; addr += xsk_frame_size; if (i == batch_size) { /* Remember len, addr, pkt_nb for next * iteration. Skipped for simplicity. */ break; } } while (len); } xsk_ring_prod__submit(&xsk->tx, i); } On the Rx path in copy mode, the xsk core copies the XDP data into multiple descriptors, if needed, and sets the XDP_PKT_CONTD flag as detailed before. Zero-copy mode in order to avoid the copies has to maintain a chain of xdp_buff_xsk structs that represent whole packet. This is because what actually is redirected is the xdp_buff and we currently have no equivalent mechanism that is used for copy mode (embedded skb_shared_info in xdp_buff) to carry the frags. This means xdp_buff_xsk grows in size but these members are at the end and should not be touched when data path is not dealing with fragmented packets. This solution kept us within assumed performance impact, hence we decided to proceed with it. When the application gets a descriptor with the XDP_PKT_CONTD flag set to one, it means that the packet consists of multiple buffers and it continues with the next buffer in the following descriptor. When a descriptor with XDP_PKT_CONTD == 0 is received, it means that this is the last buffer of the packet. AF_XDP guarantees that only a complete packet (all frames in the packet) is sent to the application. If application reads a batch of descriptors, using for example the libxdp interfaces, it is not guaranteed that the batch will end with a full packet. It might end in the middle of a packet and the rest of the buffers of that packet will arrive at the beginning of the next batch, since the libxdp interface does not read the whole ring (unless you have an enormous batch size or a very small ring size). Here is a simple Rx path pseudo-code example (using libxdp interfaces for simplicity). Error paths have been excluded for simplicity: void rx_packets(struct xsk_socket_info *xsk) { static bool new_packet = true; u32 idx_rx = 0, idx_fq = 0; static char *pkt; int rcvd = xsk_ring_cons__peek(&xsk->rx, opt_batch_size, &idx_rx); xsk_ring_prod__reserve(&xsk->umem->fq, rcvd, &idx_fq); for (int i = 0; i < rcvd; i++) { struct xdp_desc *desc = xsk_ring_cons__rx_desc(&xsk->rx, idx_rx++); char *frag = xsk_umem__get_data(xsk->umem->buffer, desc->addr); bool eop = !(desc->options & XDP_PKT_CONTD); if (new_packet) pkt = frag; else add_frag_to_pkt(pkt, frag); if (eop) process_pkt(pkt); new_packet = eop; *xsk_ring_prod__fill_addr(&xsk->umem->fq, idx_fq++) = desc->addr; } xsk_ring_prod__submit(&xsk->umem->fq, rcvd); xsk_ring_cons__release(&xsk->rx, rcvd); } We had to introduce a new bind flag (XDP_USE_SG) on the AF_XDP level to enable multi-buffer support. The reason we need to differentiate between non multi-buffer and multi-buffer is the behaviour when the kernel gets a packet that is larger than the frame size. Without multi-buffer, this packet is dropped and marked in the stats. With multi-buffer on, we want to split it up into multiple frames instead. At the start, we thought that riding on the .frags section name of the XDP program was a good idea. You do not have to introduce yet another flag and all AF_XDP users must load an XDP program anyway to get any traffic up to the socket, so why not just say that the XDP program decides if the AF_XDP socket should get multi-buffer packets or not? The problem is that we can create an AF_XDP socket that is Tx only and that works without having to load an XDP program at all. Another problem is that the XDP program might change during the execution, so we would have to check this for every single packet. Here is the observed throughput when compared to a codebase without any multi-buffer changes and measured with xdpsock for 64B packets. Apparently ZC Tx takes a hit from explicit zero length descriptors validation. Overall, in terms of ZC performance, there is a room for improvement, but for now we think this work is in a good shape in terms of correctness and functionality. We were targetting for up to 5% overhead though. Note that ZC performance drops come from core + driver support being combined, whereas copy mode had already driver support in place. Mode rxdrop l2fwd txonly ice-zc -4% -7% -6% i40e-zc -7% -6% -7% drv -1.2% 0% +2% skb -0.6% -1% +2% Thank you, Tirthendu, Magnus and Maciej Maciej Fijalkowski (8): xsk: prepare both copy and zero-copy modes to co-exist xsk: allow core/drivers to test EOP bit xsk: add new netlink attribute dedicated for ZC max frags xsk: support mbuf on ZC RX ice: xsk: add RX multi-buffer support xsk: support ZC Tx multi-buffer in batch API ice: xsk: Tx multi-buffer support selftests/xsk: reset NIC settings to default after running test suite Magnus Karlsson (7): xsk: add multi-buffer documentation selftests/xsk: transmit and receive multi-buffer packets selftests/xsk: add basic multi-buffer test selftests/xsk: add unaligned mode test for multi-buffer selftests/xsk: add invalid descriptor test for multi-buffer selftests/xsk: add metadata copy test for multi-buff selftests/xsk: add test for too many frags Tirthendu Sarkar (9): xsk: prepare 'options' in xdp_desc for multi-buffer use xsk: introduce XSK_USE_SG bind flag for xsk socket xsk: move xdp_buff's data length check to xsk_rcv_check xsk: add support for AF_XDP multi-buffer on Rx path xsk: introduce wrappers and helpers for supporting multi-buffer in Tx path xsk: add support for AF_XDP multi-buffer on Tx path xsk: discard zero length descriptors in Tx path i40e: xsk: add RX multi-buffer support i40e: xsk: add TX multi-buffer support Documentation/netlink/specs/netdev.yaml | 6 + Documentation/networking/af_xdp.rst | 211 +++++++- drivers/net/ethernet/intel/i40e/i40e_main.c | 6 +- drivers/net/ethernet/intel/i40e/i40e_txrx.c | 4 +- drivers/net/ethernet/intel/i40e/i40e_txrx.h | 2 + drivers/net/ethernet/intel/i40e/i40e_xsk.c | 101 +++- drivers/net/ethernet/intel/ice/ice_base.c | 9 +- drivers/net/ethernet/intel/ice/ice_main.c | 1 + drivers/net/ethernet/intel/ice/ice_xsk.c | 221 ++++++--- include/linux/netdevice.h | 1 + include/net/xdp_sock.h | 7 + include/net/xdp_sock_drv.h | 54 +++ include/net/xsk_buff_pool.h | 7 + include/uapi/linux/if_xdp.h | 13 + include/uapi/linux/netdev.h | 1 + net/core/dev.c | 1 + net/core/filter.c | 7 +- net/core/netdev-genl.c | 8 + net/xdp/xsk.c | 365 ++++++++++---- net/xdp/xsk_buff_pool.c | 7 + net/xdp/xsk_queue.h | 95 ++-- tools/include/uapi/linux/if_xdp.h | 9 + tools/include/uapi/linux/netdev.h | 1 + tools/lib/bpf/libbpf.h | 3 +- tools/lib/bpf/netlink.c | 5 + .../selftests/bpf/progs/xsk_xdp_progs.c | 6 +- tools/testing/selftests/bpf/test_xsk.sh | 5 + tools/testing/selftests/bpf/xsk.c | 136 +++++- tools/testing/selftests/bpf/xsk.h | 2 + tools/testing/selftests/bpf/xsk_prereqs.sh | 7 + tools/testing/selftests/bpf/xskxceiver.c | 458 +++++++++++++++--- tools/testing/selftests/bpf/xskxceiver.h | 21 +- 32 files changed, 1505 insertions(+), 275 deletions(-)