This patchset adds support for zero copy rx into userspace pages using io_uring, eliminating a kernel to user copy. We configure a page pool that a driver uses to fill a hw rx queue to hand out user pages instead of kernel pages. Any data that ends up hitting this hw rx queue will thus be dma'd into userspace memory directly, without needing to be bounced through kernel memory. 'Reading' data out of a socket instead becomes a _notification_ mechanism, where the kernel tells userspace where the data is. The overall approach is similar to the devmem TCP proposal. This relies on hw header/data split, flow steering and RSS to ensure packet headers remain in kernel memory and only desired flows hit a hw rx queue configured for zero copy. Configuring this is outside of the scope of this patchset. We share netdev core infra with devmem TCP. The main difference is that io_uring is used for the uAPI and the lifetime of all objects are bound to an io_uring instance. Data is 'read' using a new io_uring request type. When done, data is returned via a new shared refill queue. A zero copy page pool refills a hw rx queue from this refill queue directly. Of course, the lifetime of these data buffers are managed by io_uring rather than the networking stack, with different refcounting rules. This patchset is the first step adding basic zero copy support. We will extend this iteratively with new features e.g. dynamically allocated zero copy areas, THP support, dmabuf support, improved copy fallback, general optimisations and more. In terms of netdev support, we're first targeting Broadcom bnxt. Patches aren't included since Taehee Yoo has already sent a more comprehensive patchset adding support in [1]. Google gve should already support this, and Mellanox mlx5 support is WIP pending driver changes. ============ Pull Request ============ The following changes since commit d22f955cc2cb9684dd45396f974101f288869485: rust: net::phy scope ThisModule usage in the module_phy_driver macro (2024-12-17 13:30:45 +0100) are available in the Git repository at: https://github.com/spikeh/linux zcrx/v9 for you to fetch changes up to ea606d17b90b853c8c72d490daaccfb81adce3b8: io_uring/zcrx: add selftest (2024-12-17 16:26:02 -0800) =========== Performance =========== Note: Comparison with epoll + TCP_ZEROCOPY_RECEIVE isn't done yet. Test setup: * AMD EPYC 9454 * Broadcom BCM957508 200G * Kernel v6.11 base [2] * liburing fork [3] * kperf fork [4] * 4K MTU * Single TCP flow With application thread + net rx softirq pinned to _different_ cores: +-------------------------------+ | epoll | io_uring | |-----------|-------------------| | 82.2 Gbps | 116.2 Gbps (+41%) | +-------------------------------+ Pinned to _same_ core: +-------------------------------+ | epoll | io_uring | |-----------|-------------------| | 62.6 Gbps | 80.9 Gbps (+29%) | +-------------------------------+ ===== Links ===== Broadcom bnxt support: [1]: https://lore.kernel.org/netdev/20241003160620.1521626-8-ap420073@xxxxxxxxx/ Linux kernel branch: [2]: https://github.com/spikeh/linux.git zcrx/v9 liburing for testing: [3]: https://github.com/isilence/liburing.git zcrx/next kperf for testing: [4]: https://git.kernel.dk/kperf.git Changes in v9: -------------- * Fail proof against multiple page pools running the same memory provider * Lock the consumer side of the refill queue. * Move scrub into io_uring exit. * Kill napi_execute. * Kill area init api and export finer grained net helpers as partial init now need to happen in ->alloc_netmems() * Separate user refcounting. * Fix copy fallback path math. * Add rodata check to page_pool_init() * Fix incorrect path in documentation Changes in v8: -------------- * add documentation and selftest * use io_uring regions for the refill ring Changes in v7: -------------- net: * Use NAPI_F_PREFER_BUSY_POLL for napi_execute + stylistics changes. Changes in v6: -------------- Please note: Comparison with TCP_ZEROCOPY_RECEIVE isn't done yet. net: * Drop a devmem.h clean up patch. * Migrate to netdev_get_by_index from deprecated API. * Fix !CONFIG_NET_DEVMEM build. * Don’t return into the page pool cache directly, use a new helper * Refactor napi_execute io_uring: * Require IORING_RECV_MULTISHOT flag set. * Add unselectable CONFIG_IO_URING_ZCRX. * Pulled latest io_uring changes. * Unexport io_uring_pp_zc_ops. Changes in v5: -------------- * Rebase on top of merged net_iov + netmem infra. * Decouple net_iov from devmem TCP. * Use netdev queue API to allocate an rx queue. * Minor uAPI enhancements for future extensibility. * QoS improvements with request throttling. Changes in RFC v4: ------------------ * Rebased on top of Mina Almasry's TCP devmem patchset and latest net-next, now sharing common infra e.g.: * netmem_t and net_iovs * Page pool memory provider * The registered buffer (rbuf) completion queue where completions from io_recvzc requests are posted is removed. Now these post into the main completion queue, using big (32-byte) CQEs. The first 16 bytes is an ordinary CQE, while the latter 16 bytes contain the io_uring_rbuf_cqe as before. This vastly simplifies the uAPI and removes a level of indirection in userspace when looking for payloads. * The rbuf refill queue is still needed for userspace to return buffers to kernel. * Simplified code and uAPI on the io_uring side, particularly io_recvzc() and io_zc_rx_recv(). Many unnecessary lines were removed e.g. extra msg flags, readlen, etc. 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. David Wei (7): io_uring/zcrx: add interface queue and refill queue io_uring/zcrx: add io_zcrx_area net: page pool: export page_pool_set_dma_addr_netmem() io_uring/zcrx: add io_recvzc request io_uring/zcrx: set pp memory provider for an rx queue net: add documentation for io_uring zcrx io_uring/zcrx: add selftest Jakub Kicinski (1): net: page_pool: create hooks for custom page providers Pavel Begunkov (13): net: page_pool: don't cast mp param to devmem net: prefix devmem specific helpers net: generalise net_iov chunk owners net: page_pool: add mp op for netlink reporting net: page_pool: add a mp hook to unregister_netdevice* net: prepare for non devmem TCP memory providers net: expose page_pool_{set,clear}_pp_info net: page_pool: introduce page_pool_mp_return_in_cache io_uring/zcrx: grab a net device io_uring/zcrx: dma-map area for the device io_uring/zcrx: implement zerocopy receive pp memory provider io_uring/zcrx: throttle receive requests io_uring/zcrx: add copy fallback Documentation/networking/index.rst | 1 + Documentation/networking/iou-zcrx.rst | 201 ++++ Kconfig | 2 + include/linux/io_uring_types.h | 6 + include/net/netmem.h | 21 +- include/net/page_pool/helpers.h | 20 + include/net/page_pool/types.h | 13 + include/uapi/linux/io_uring.h | 54 +- include/uapi/linux/netdev.h | 1 + io_uring/KConfig | 10 + io_uring/Makefile | 1 + io_uring/io_uring.c | 7 + io_uring/io_uring.h | 10 + io_uring/memmap.h | 1 + io_uring/net.c | 74 ++ io_uring/opdef.c | 16 + io_uring/register.c | 7 + io_uring/rsrc.c | 2 +- io_uring/rsrc.h | 1 + io_uring/zcrx.c | 936 ++++++++++++++++++ io_uring/zcrx.h | 71 ++ net/core/dev.c | 16 +- net/core/devmem.c | 91 +- net/core/devmem.h | 50 +- net/core/page_pool.c | 53 +- net/core/page_pool_priv.h | 26 - net/core/page_pool_user.c | 5 +- net/ipv4/tcp.c | 7 +- .../selftests/drivers/net/hw/.gitignore | 2 + .../testing/selftests/drivers/net/hw/Makefile | 6 + .../selftests/drivers/net/hw/iou-zcrx.c | 432 ++++++++ .../selftests/drivers/net/hw/iou-zcrx.py | 64 ++ 32 files changed, 2104 insertions(+), 103 deletions(-) create mode 100644 Documentation/networking/iou-zcrx.rst create mode 100644 io_uring/KConfig create mode 100644 io_uring/zcrx.c create mode 100644 io_uring/zcrx.h create mode 100644 tools/testing/selftests/drivers/net/hw/iou-zcrx.c create mode 100755 tools/testing/selftests/drivers/net/hw/iou-zcrx.py -- 2.43.5
