[RFC PATCH v3 00/20] Zero copy Rx using io_uring

David Wei
2023-12-19T21:04:05Z

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.

Full kernel tree including some out of tree BNXT changes:

https://github.com/spikeh/linux/tree/zcrx_sil

On the userspace side, support is added to both liburing and Netbench:

https://github.com/spikeh/liburing/tree/zcrx2
https://github.com/spikeh/netbench/tree/zcrx

Hardware support is added to the Broadcom BNXT driver. 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.
Build Netbench using the modified liburing above.

This patchset is based on the work by Jonathan Lemon
<jonathan.lemon@gmail.com>:
https://lore.kernel.org/io-uring/20221108050521.3198458-1-jonathan.lemon@gmail.com/

Changes in RFC v3:
------------------

* Rebased on top of Jakub Kicinski's memory provider API RFC. The ZC
pool added is now a backend for memory provider.
* We're also reusing ppiov infrastructure. The refcounting rules stay
the same but it's shifted into ppiov->refcount. That lets us to
flexibly manage buffer lifetimes without adding any extra code to the
common networking paths. It'd also make it easier to support dmabufs
and device memory in the future.
* io_uring also knows about pages, and so ppiovs might unnecessarily
break tools inspecting data, that can easily be solved later.

Many patches are not for upstream as they depend on work in progress,
namely from Mina:

* struct netmem_t
* Driver ndo commands for Rx queue configs
* struct page_pool_iov and shared pp infra

Changes in RFC v2:
------------------

* Added copy fallback support if userspace memory allocated for ZC Rx
runs out, or if header splitting or flow steering fails.
* Added veth support for ZC Rx, for testing and demonstration. We will
need to figure out what driver would be best for such testing
functionality in the future. Perhaps netdevsim?
* Added socket registration API to io_uring to associate specific
sockets with ifqs/Rx queues for ZC.
* Added multi-socket support, such that multiple connections can be
steered into the same hardware Rx queue.
* Added Netbench server/client support.

Known deficiencies that we will address in a future patchset:

* Proper test driver + selftests, maybe netdevsim.
* Revisiting userspace API.
* Multi-region support.
* Steering setup.
* Further optimisation work.
* ...and more.

If you would like to try out this patchset, build and run the kernel
tree then build Netbench using liburing, all from forks above.

Run setup.sh first:

https://gist.github.com/isilence/e6a28ce41a545a261566672104afa461

Then run the following commands:

sudo ip netns exec nsserv ./netbench --server_only 1 --v6 false \
--rx "io_uring --provide_buffers 0 --use_zc 1 \
--zc_pool_pages 16384 --zc_ifname ptp-serv" --use_port 9999

sudo ip netns exec nscl ./netbench --client_only 1 --v6 false \
--tx "epoll --threads 1 --per_thread 1 --size 2800" \
--host 10.10.10.20 --use_port 9999

David Wei (6):
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 io_recvzc request

Pavel Begunkov (14):
net: page_pool: add ppiov mangling helper
tcp: don't allow non-devmem originated ppiov
net: page pool: rework ppiov life cycle
net: enable napi_pp_put_page for ppiov
net: page_pool: add ->scrub mem provider callback
io_uring: separate header for exported net bits
io_uring/zcrx: implement socket registration
io_uring: implement pp memory provider for zc rx
net: page pool: add io_uring memory provider
net: execute custom callback from napi
io_uring/zcrx: add copy fallback
veth: add support for io_uring zc rx
net: page pool: generalise ppiov dma address get
bnxt: enable io_uring zc page pool

drivers/net/ethernet/broadcom/bnxt/bnxt.c | 71 +-
drivers/net/ethernet/broadcom/bnxt/bnxt.h | 7 +
drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c | 3 +
drivers/net/veth.c | 211 +++-
include/linux/io_uring.h | 6 -
include/linux/io_uring/net.h | 31 +
include/linux/io_uring_types.h | 8 +
include/linux/net.h | 2 +
include/linux/netdevice.h | 6 +
include/net/busy_poll.h | 7 +
include/net/page_pool/helpers.h | 27 +-
include/net/page_pool/types.h | 4 +
include/uapi/linux/io_uring.h | 61 ++
io_uring/Makefile | 2 +-
io_uring/io_uring.c | 24 +
io_uring/net.c | 133 ++-
io_uring/opdef.c | 16 +
io_uring/uring_cmd.c | 1 +
io_uring/zc_rx.c | 954 ++++++++++++++++++
io_uring/zc_rx.h | 80 ++
net/core/dev.c | 46 +
net/core/page_pool.c | 68 +-
net/core/skbuff.c | 28 +-
net/ipv4/tcp.c | 7 +
net/socket.c | 3 +-
25 files changed, 1737 insertions(+), 69 deletions(-)
create mode 100644 include/linux/io_uring/net.h
create mode 100644 io_uring/zc_rx.c
create mode 100644 io_uring/zc_rx.h

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2.39.3