On Thu, 15 Aug 2019 at 18:46, Samudrala, Sridhar <sridhar.samudrala@xxxxxxxxx> wrote: > > On 8/15/2019 5:51 AM, Björn Töpel wrote: > > On 2019-08-15 05:46, Sridhar Samudrala wrote: > >> This patch series introduces XDP_SKIP_BPF flag that can be specified > >> during the bind() call of an AF_XDP socket to skip calling the BPF > >> program in the receive path and pass the buffer directly to the socket. > >> > >> When a single AF_XDP socket is associated with a queue and a HW > >> filter is used to redirect the packets and the app is interested in > >> receiving all the packets on that queue, we don't need an additional > >> BPF program to do further filtering or lookup/redirect to a socket. > >> > >> Here are some performance numbers collected on > >> - 2 socket 28 core Intel(R) Xeon(R) Platinum 8180 CPU @ 2.50GHz > >> - Intel 40Gb Ethernet NIC (i40e) > >> > >> All tests use 2 cores and the results are in Mpps. > >> > >> turbo on (default) > >> --------------------------------------------- > >> no-skip-bpf skip-bpf > >> --------------------------------------------- > >> rxdrop zerocopy 21.9 38.5 > >> l2fwd zerocopy 17.0 20.5 > >> rxdrop copy 11.1 13.3 > >> l2fwd copy 1.9 2.0 > >> > >> no turbo : echo 1 > /sys/devices/system/cpu/intel_pstate/no_turbo > >> --------------------------------------------- > >> no-skip-bpf skip-bpf > >> --------------------------------------------- > >> rxdrop zerocopy 15.4 29.0 > >> l2fwd zerocopy 11.8 18.2 > >> rxdrop copy 8.2 10.5 > >> l2fwd copy 1.7 1.7 > >> --------------------------------------------- > >> > > > > This work is somewhat similar to the XDP_ATTACH work [1]. Avoiding the > > retpoline in the XDP program call is a nice performance boost! I like > > the numbers! :-) I also like the idea of adding a flag that just does > > what most AF_XDP Rx users want -- just getting all packets of a > > certain queue into the XDP sockets. > > > > In addition to Toke's mail, I have some more concerns with the series: > > > > * AFAIU the SKIP_BPF only works for zero-copy enabled sockets. IMO, it > > should work for all modes (including XDP_SKB). > > This patch enables SKIP_BPF for AF_XDP sockets where an XDP program is > attached at driver level (both zerocopy and copy modes) > I tried a quick hack to see the perf benefit with generic XDP mode, but > i didn't see any significant improvement in performance in that > scenario. so i didn't include that mode. > > > > > * In order to work, a user still needs an XDP program running. That's > > clunky. I'd like the behavior that if no XDP program is attached, > > and the option is set, the packets for a that queue end up in the > > socket. If there's an XDP program attached, the program has > > precedence. > > I think this would require more changes in the drivers to take XDP > datapath even when there is no XDP program loaded. > Today, from a driver perspective, to enable XDP you pass a struct bpf_prog pointer via the ndo_bpf. The program get executed in BPF_PROG_RUN (via bpf_prog_run_xdp) from include/linux/filter.h. I think it's possible to achieve what you're doing w/o *any* driver modification. Pass a special, invalid, pointer to the driver (say (void *)0x1 or smth more elegant), which has a special handling in BPF_RUN_PROG e.g. setting a per-cpu state and return XDP_REDIRECT. The per-cpu state is picked up in xdp_do_redirect and xdp_flush. An approach like this would be general, and apply to all modes automatically. Thoughts? > > > > * It requires changes in all drivers. Not nice, and scales badly. Try > > making it generic (xdp_do_redirect/xdp_flush), so it Just Works for > > all XDP capable drivers. > > I tried to make this as generic as possible and make the changes to the > driver very minimal, but could not find a way to avoid any changes at > all to the driver. xdp_do_direct() gets called based after the call to > bpf_prog_run_xdp() in the drivers. > > > > > Thanks for working on this! > > > > > > Björn > > > > [1] > > https://lore.kernel.org/netdev/20181207114431.18038-1-bjorn.topel@xxxxxxxxx/ > > > > > > > >> Sridhar Samudrala (5): > >> xsk: Convert bool 'zc' field in struct xdp_umem to a u32 bitmap > >> xsk: Introduce XDP_SKIP_BPF bind option > >> i40e: Enable XDP_SKIP_BPF option for AF_XDP sockets > >> ixgbe: Enable XDP_SKIP_BPF option for AF_XDP sockets > >> xdpsock_user: Add skip_bpf option > >> > >> drivers/net/ethernet/intel/i40e/i40e_txrx.c | 22 +++++++++- > >> drivers/net/ethernet/intel/i40e/i40e_xsk.c | 6 +++ > >> drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 20 ++++++++- > >> drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c | 16 ++++++- > >> include/net/xdp_sock.h | 21 ++++++++- > >> include/uapi/linux/if_xdp.h | 1 + > >> include/uapi/linux/xdp_diag.h | 1 + > >> net/xdp/xdp_umem.c | 9 ++-- > >> net/xdp/xsk.c | 43 ++++++++++++++++--- > >> net/xdp/xsk_diag.c | 5 ++- > >> samples/bpf/xdpsock_user.c | 8 ++++ > >> 11 files changed, 135 insertions(+), 17 deletions(-) > >> > _______________________________________________ > Intel-wired-lan mailing list > Intel-wired-lan@xxxxxxxxxx > https://lists.osuosl.org/mailman/listinfo/intel-wired-lan
