From: David Wei <davidhwei@xxxxxxxx> This patchset is a proposal that adds zero copy network RX to io_uring. With it, userspace can register a region of host memory for receiving data directly from a NIC using DMA, without needing a kernel to user copy. Software support is added to the Broadcom BNXT driver. Hardware support for receive flow steering and header splitting is required. On the userspace side, a sample server is added in this branch of liburing: https://github.com/spikeh/liburing/tree/zcrx2 Build liburing as normal, and run examples/zcrx. Then, set flow steering rules using ethtool. A sample shell script is included in examples/zcrx_flow.sh, but you need to change the source IP. Finally, connect a client using e.g. netcat and send data. This patchset + userspace code was tested on an Intel Xeon Platinum 8321HC CPU and Broadcom BCM57504 NIC. Early benchmarks using this prototype, with iperf3 as a load generator, showed a ~50% reduction in overall system memory bandwidth as measured using perf counters. Note that DDIO must be disabled on Intel systems. Mina et al. from Google and Kuba are collaborating on a similar proposal to ZC from NIC to devmem. There are many shared functionality in netdev that we can collaborate on e.g.: * Page pool memory provider backend and resource registration * Page pool refcounted iov/buf representation and lifecycle * Setting receive flow steering As mentioned earlier, this is an early prototype. It is brittle, some functionality is missing and there's little optimisation. We're looking for feedback on the overall approach and points of collaboration in netdev. * No copy fallback, if payload ends up in linear part of skb then the code will not work * No way to pin an RX queue to a specific CPU * Only one ifq, one pool region, on RX queue... This patchset is based on the work by Jonathan Lemon <jonathan.lemon@xxxxxxxxx>: https://lore.kernel.org/io-uring/20221108050521.3198458-1-jonathan.lemon@xxxxxxxxx/ David Wei (11): io_uring: add interface queue io_uring: add mmap support for shared ifq ringbuffers netdev: add XDP_SETUP_ZC_RX command io_uring: setup ZC for an RX queue when registering an ifq io_uring: add ZC buf and pool io_uring: add ZC pool API skbuff: add SKBFL_FIXED_FRAG and skb_fixed() io_uring: allocate a uarg for freeing zero copy skbs io_uring: delay ZC pool destruction netdev/bnxt: add data pool and use it in BNXT driver io_uring: add io_recvzc request drivers/net/ethernet/broadcom/bnxt/bnxt.c | 59 +- drivers/net/ethernet/broadcom/bnxt/bnxt.h | 4 + drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c | 3 + include/linux/io_uring.h | 31 + include/linux/io_uring_types.h | 6 + include/linux/netdevice.h | 11 + include/linux/skbuff.h | 10 +- include/net/data_pool.h | 96 +++ include/uapi/linux/io_uring.h | 53 ++ io_uring/Makefile | 3 +- io_uring/io_uring.c | 13 + io_uring/kbuf.c | 30 + io_uring/kbuf.h | 5 + io_uring/net.c | 83 +- io_uring/opdef.c | 16 + io_uring/zc_rx.c | 723 ++++++++++++++++++ io_uring/zc_rx.h | 42 + 17 files changed, 1168 insertions(+), 20 deletions(-) create mode 100644 include/net/data_pool.h create mode 100644 io_uring/zc_rx.c create mode 100644 io_uring/zc_rx.h -- 2.39.3
