From patchwork Thu Aug 10 01:57:36 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Mina Almasry X-Patchwork-Id: 713026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9455EEB64DD for ; Thu, 10 Aug 2023 01:58:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229746AbjHJB6A (ORCPT ); Wed, 9 Aug 2023 21:58:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49984 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229604AbjHJB6A (ORCPT ); Wed, 9 Aug 2023 21:58:00 -0400 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 06FE61982 for ; Wed, 9 Aug 2023 18:57:59 -0700 (PDT) Received: by mail-yb1-xb4a.google.com with SMTP id 3f1490d57ef6-c5fc972760eso437104276.1 for ; Wed, 09 Aug 2023 18:57:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1691632678; x=1692237478; h=content-transfer-encoding:cc:to:from:subject:message-id :mime-version:date:from:to:cc:subject:date:message-id:reply-to; bh=C1eUR+i8ywidiH3Q/hZ5RblhFb7NEutEyHCiHQNNJFs=; b=KtezmRX6B/be0QfAMpUbeEwFXA3taU6DiclFDTRM3WYFX6tlgjBSs7T+00SKqYYiDO 7ouOum4rt/r91Q9cFGZKgmHfZhElzuydgtT1lih9tWRgpU+GvhwxcUW54EI8TgE0OTRE THaH5QJMkTy9c2R8Q0lUqtMj39qCXGMMBblGNjeQkCim5gjoiJFxcJJDR4eNg2Vpy1PV U4BaJqB8xsd0bxrgy2LXPIPNa6YukB80Ha1p2UHK8d0ZucyC557QPhHyAn01jX92m6tL cTrwc8Zl0K8HyCNzugUzTCfey5ptmYi+IGCwO6ztd73vtXPfvm8YJ3mpEzR8JCh5lJuz F/jg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1691632678; x=1692237478; h=content-transfer-encoding:cc:to:from:subject:message-id :mime-version:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=C1eUR+i8ywidiH3Q/hZ5RblhFb7NEutEyHCiHQNNJFs=; b=cr088y76vVopdHvgKt4D/UZcl86TJkEVsdxDDyoS7VxgzwBm21DmpVQsAcCY1gnJ+1 Ke/p3fOXVDx6AfgR4fGIZPIGcjA5uEQppYlKkOt6fqLkzrPOjgw8Gou2sT7E40rpHmBK 5bTXhDJ6shXyDwHwIvJ0ZKbEbw+XbAGcToCfD8LX79ndWF1fL5DcsxWlq2TXGK5co8ej 1RucxuQC1ptcEN6L22Gt1d2466OXxAWewOx+/YxF++N0dRgV7uVp3jOPMIPo4OUmOCp5 8M7uk1vamzKnHomhZfdsf5NYGDCzrC6pt4SRD3H/+5bGDdojlN8RgAjScjk18tromgFR Z4Dw== X-Gm-Message-State: AOJu0YwC4DbwlkaOnda3191qQD+vnuboqDPgkCZO0IHXdjKZ7qo7cggt rMbPslyAkDmnOllTM+Rrfh13Ant22LWimQB+TQ== X-Google-Smtp-Source: AGHT+IEHRcXmliHnBk1RHJNGGa5HzyhaqUgdTmjX5FtiHcMdwonj8qLg/el37HVywankDq3LaPvjaelxJFP2NKgeEg== X-Received: from almasrymina.svl.corp.google.com ([2620:15c:2c4:200:73ad:9ed5:e067:2b9b]) (user=almasrymina job=sendgmr) by 2002:a25:cb89:0:b0:d5d:b03c:49b2 with SMTP id b131-20020a25cb89000000b00d5db03c49b2mr19668ybg.11.1691632678141; Wed, 09 Aug 2023 18:57:58 -0700 (PDT) Date: Wed, 9 Aug 2023 18:57:36 -0700 Mime-Version: 1.0 X-Mailer: git-send-email 2.41.0.640.ga95def55d0-goog Message-ID: <20230810015751.3297321-1-almasrymina@google.com> Subject: [RFC PATCH v2 00/11] Device Memory TCP From: Mina Almasry To: netdev@vger.kernel.org, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org Cc: Mina Almasry , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Jesper Dangaard Brouer , Ilias Apalodimas , Arnd Bergmann , David Ahern , Willem de Bruijn , Sumit Semwal , " =?utf-8?q?Christian_K=C3=B6nig?= " , Jason Gunthorpe , Hari Ramakrishnan , Dan Williams , Andy Lutomirski , stephen@networkplumber.org, sdf@google.com Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org Changes in RFC v2: ------------------ The sticking point in RFC v1[1] was the dma-buf pages approach we used to deliver the device memory to the TCP stack. RFC v2 is a proof-of-concept that attempts to resolve this by implementing scatterlist support in the networking stack, such that we can import the dma-buf scatterlist directly. This is the approach proposed at a high level here[2]. Detailed changes: 1. Replaced dma-buf pages approach with importing scatterlist into the page pool. 2. Replace the dma-buf pages centric API with a netlink API. 3. Removed the TX path implementation - there is no issue with implementing the TX path with scatterlist approach, but leaving out the TX path makes it easier to review. 4. Functionality is tested with this proposal, but I have not conducted perf testing yet. I'm not sure there are regressions, but I removed perf claims from the cover letter until they can be re-confirmed. 5. Added Signed-off-by: contributors to the implementation. 6. Fixed some bugs with the RX path since RFC v1. Any feedback welcome, but specifically the biggest pending questions needing feedback IMO are: 1. Feedback on the scatterlist-based approach in general. 2. Netlink API (Patch 1 & 2). 3. Approach to handle all the drivers that expect to receive pages from the page pool (Patch 6). [1] https://lore.kernel.org/netdev/dfe4bae7-13a0-3c5d-d671-f61b375cb0b4@gmail.com/T/ [2] https://lore.kernel.org/netdev/CAHS8izPm6XRS54LdCDZVd0C75tA1zHSu6jLVO8nzTLXCc=H7Nw@mail.gmail.com/ ---------------------- * TL;DR: Device memory TCP (devmem TCP) is a proposal for transferring data to and/or from device memory efficiently, without bouncing the data to a host memory buffer. * Problem: A large amount of data transfers have device memory as the source and/or destination. Accelerators drastically increased the volume of such transfers. Some examples include: - ML accelerators transferring large amounts of training data from storage into GPU/TPU memory. In some cases ML training setup time can be as long as 50% of TPU compute time, improving data transfer throughput & efficiency can help improving GPU/TPU utilization. - Distributed training, where ML accelerators, such as GPUs on different hosts, exchange data among them. - Distributed raw block storage applications transfer large amounts of data with remote SSDs, much of this data does not require host processing. Today, the majority of the Device-to-Device data transfers the network are implemented as the following low level operations: Device-to-Host copy, Host-to-Host network transfer, and Host-to-Device copy. The implementation is suboptimal, especially for bulk data transfers, and can put significant strains on system resources, such as host memory bandwidth, PCIe bandwidth, etc. One important reason behind the current state is the kernel’s lack of semantics to express device to network transfers. * Proposal: In this patch series we attempt to optimize this use case by implementing socket APIs that enable the user to: 1. send device memory across the network directly, and 2. receive incoming network packets directly into device memory. Packet _payloads_ go directly from the NIC to device memory for receive and from device memory to NIC for transmit. Packet _headers_ go to/from host memory and are processed by the TCP/IP stack normally. The NIC _must_ support header split to achieve this. Advantages: - Alleviate host memory bandwidth pressure, compared to existing network-transfer + device-copy semantics. - Alleviate PCIe BW pressure, by limiting data transfer to the lowest level of the PCIe tree, compared to traditional path which sends data through the root complex. * Patch overview: ** Part 1: netlink API Gives user ability to bind dma-buf to an RX queue. ** Part 2: scatterlist support Currently the standard for device memory sharing is DMABUF, which doesn't generate struct pages. On the other hand, networking stack (skbs, drivers, and page pool) operate on pages. We have 2 options: 1. Generate struct pages for dmabuf device memory, or, 2. Modify the networking stack to process scatterlist. Approach #1 was attempted in RFC v1. RFC v2 implements approach #2. ** part 3: page pool support We piggy back on page pool memory providers proposal: https://github.com/kuba-moo/linux/tree/pp-providers It allows the page pool to define a memory provider that provides the page allocation and freeing. It helps abstract most of the device memory TCP changes from the driver. ** part 4: support for unreadable skb frags Page pool iovs are not accessible by the host; we implement changes throughput the networking stack to correctly handle skbs with unreadable frags. ** Part 5: recvmsg() APIs We define user APIs for the user to send and receive device memory. Not included with this RFC is the GVE devmem TCP support, just to simplify the review. Code available here if desired: https://github.com/mina/linux/tree/tcpdevmem This RFC is built on top of net-next with Jakub's pp-providers changes cherry-picked. * NIC dependencies: 1. (strict) Devmem TCP require the NIC to support header split, i.e. the capability to split incoming packets into a header + payload and to put each into a separate buffer. Devmem TCP works by using device memory for the packet payload, and host memory for the packet headers. 2. (optional) Devmem TCP works better with flow steering support & RSS support, i.e. the NIC's ability to steer flows into certain rx queues. This allows the sysadmin to enable devmem TCP on a subset of the rx queues, and steer devmem TCP traffic onto these queues and non devmem TCP elsewhere. The NIC I have access to with these properties is the GVE with DQO support running in Google Cloud, but any NIC that supports these features would suffice. I may be able to help reviewers bring up devmem TCP on their NICs. * Testing: The series includes a udmabuf kselftest that show a simple use case of devmem TCP and validates the entire data path end to end without a dependency on a specific dmabuf provider. ** Test Setup Kernel: net-next with this RFC and memory provider API cherry-picked locally. Hardware: Google Cloud A3 VMs. NIC: GVE with header split & RSS & flow steering support. Mina Almasry (11): net: add netdev netlink api to bind dma-buf to a net device netdev: implement netlink api to bind dma-buf to netdevice netdev: implement netdevice devmem allocator memory-provider: updates to core provider API for devmem TCP memory-provider: implement dmabuf devmem memory provider page-pool: add device memory support net: support non paged skb frags net: add support for skbs with unreadable frags tcp: implement recvmsg() RX path for devmem TCP net: add SO_DEVMEM_DONTNEED setsockopt to release RX pages selftests: add ncdevmem, netcat for devmem TCP Documentation/netlink/specs/netdev.yaml | 27 ++ include/linux/netdevice.h | 61 +++ include/linux/skbuff.h | 54 ++- include/linux/socket.h | 1 + include/net/page_pool.h | 186 ++++++++- include/net/sock.h | 2 + include/net/tcp.h | 5 +- include/uapi/asm-generic/socket.h | 6 + include/uapi/linux/netdev.h | 10 + include/uapi/linux/uio.h | 10 + net/core/datagram.c | 6 + net/core/dev.c | 214 ++++++++++ net/core/gro.c | 2 +- net/core/netdev-genl-gen.c | 14 + net/core/netdev-genl-gen.h | 1 + net/core/netdev-genl.c | 103 +++++ net/core/page_pool.c | 171 ++++++-- net/core/skbuff.c | 80 +++- net/core/sock.c | 36 ++ net/ipv4/tcp.c | 196 ++++++++- net/ipv4/tcp_input.c | 13 +- net/ipv4/tcp_ipv4.c | 7 + net/ipv4/tcp_output.c | 5 +- net/packet/af_packet.c | 4 +- tools/include/uapi/linux/netdev.h | 10 + tools/net/ynl/generated/netdev-user.c | 41 ++ tools/net/ynl/generated/netdev-user.h | 46 ++ tools/testing/selftests/net/.gitignore | 1 + tools/testing/selftests/net/Makefile | 5 + tools/testing/selftests/net/ncdevmem.c | 534 ++++++++++++++++++++++++ 30 files changed, 1787 insertions(+), 64 deletions(-) create mode 100644 tools/testing/selftests/net/ncdevmem.c