[v2,0/3] AF_XDP Preferred Busy Polling
Message ID | 20210309101958.27355-1-ciara.loftus@intel.com (mailing list archive) |
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Headers |
Return-Path: <dev-bounces@dpdk.org> X-Original-To: patchwork@inbox.dpdk.org Delivered-To: patchwork@inbox.dpdk.org Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124]) by inbox.dpdk.org (Postfix) with ESMTP id 551FDA0567; Tue, 9 Mar 2021 11:50:49 +0100 (CET) Received: from [217.70.189.124] (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id BA68622A4D8; Tue, 9 Mar 2021 11:50:48 +0100 (CET) Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by mails.dpdk.org (Postfix) with ESMTP id 370E522A498 for <dev@dpdk.org>; Tue, 9 Mar 2021 11:50:47 +0100 (CET) IronPort-SDR: siStQV6P9nx0KOSB5VBVBb/QMqvG+cXDjOHLWuWKU5AaJTGC2m6bf34byCOVH6KqbwWL2i+ovE +5R4HtXOYN0w== X-IronPort-AV: E=McAfee;i="6000,8403,9917"; a="168118940" X-IronPort-AV: E=Sophos;i="5.81,234,1610438400"; d="scan'208";a="168118940" Received: from orsmga006.jf.intel.com ([10.7.209.51]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Mar 2021 02:50:46 -0800 IronPort-SDR: AzVIYGBpTC27RGcg1+iYWd4Ez+pHMGTM3HDcvESeQQ7TquDOuoDVhVq+6Becqwb1OUqsz++xUS GTHQLI21d6xw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.81,234,1610438400"; d="scan'208";a="371499372" Received: from silpixa00399839.ir.intel.com (HELO localhost.localdomain) ([10.237.222.142]) by orsmga006.jf.intel.com with ESMTP; 09 Mar 2021 02:50:44 -0800 From: Ciara Loftus <ciara.loftus@intel.com> To: dev@dpdk.org Cc: Ciara Loftus <ciara.loftus@intel.com> Date: Tue, 9 Mar 2021 10:19:55 +0000 Message-Id: <20210309101958.27355-1-ciara.loftus@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20210224111852.11947-1-ciara.loftus@intel.com> References: <20210224111852.11947-1-ciara.loftus@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Subject: [dpdk-dev] [PATCH v2 0/3] AF_XDP Preferred Busy Polling X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions <dev.dpdk.org> List-Unsubscribe: <https://mails.dpdk.org/options/dev>, <mailto:dev-request@dpdk.org?subject=unsubscribe> List-Archive: <http://mails.dpdk.org/archives/dev/> List-Post: <mailto:dev@dpdk.org> List-Help: <mailto:dev-request@dpdk.org?subject=help> List-Subscribe: <https://mails.dpdk.org/listinfo/dev>, <mailto:dev-request@dpdk.org?subject=subscribe> Errors-To: dev-bounces@dpdk.org Sender: "dev" <dev-bounces@dpdk.org> |
Message
Loftus, Ciara
March 9, 2021, 10:19 a.m. UTC
Single-core performance of AF_XDP at high loads can be poor because a heavily loaded NAPI context will never enter or allow for busy-polling. 1C testpmd rxonly (both IRQs and PMD on core 0): ./dpdk-testpmd -l 0-1 --vdev=net_af_xdp0,iface=eth0 --main-lcore=1 -- \ --forward-mode=rxonly 0.088Mpps In order to achieve decent performance at high loads, it is currently recommended ensure the IRQs for the netdev queue and the core running the PMD are different. 2C testpmd rxonly (IRQs on core 0, PMD on core 1): ./dpdk-testpmd -l 0-1 --vdev=net_af_xdp0,iface=eth0 --main-lcore=0 -- \ --forward-mode=rxonly 19.26Mpps However using an extra core is of course not ideal. The SO_PREFER_BUSY_POLL socket option was introduced in kernel v5.11 to help improve 1C performance. See [1]. This series sets this socket option on xsks created with DPDK (ie. instances of the AF_XDP PMD) unless explicitly disabled or not supported by the kernel. It was chosen to be enabled by default in order to bring the AF_XDP PMD in line with most other PMDs which execute on a single core. The following system and netdev settings are recommended in conjunction with busy polling: echo 2 | sudo tee /sys/class/net/eth0/napi_defer_hard_irqs echo 200000 | sudo tee /sys/class/net/eth0/gro_flush_timeout Re-running the 1C test with busy polling support and the above settings: ./dpdk-testpmd -l 0-1 --vdev=net_af_xdp0,iface=eth0 --main-lcore=1 -- \ --forward-mode=rxonly 10.45Mpps A new vdev arg is introduced called 'busy_budget' whose default value is 64. busy_budget is the value supplied to the kernel with the SO_BUSY_POLL_BUDGET socket option and represents the busy-polling NAPI budget ie. the number of packets the kernel will attempt to process in the netdev's NAPI context. To set the busy budget to 256: ./dpdk-testpmd --vdev=net_af_xdp0,iface=eth0,busy_budget=256 14.06Mpps If you still wish to run using 2 cores (one for PMD once for IRQs) it is recommended to disable busy polling to achieve optimal 2C performance: ./dpdk-testpmd --vdev=net_af_xdp0,iface=eth0,busy_budget=0 19.09Mpps v1->v2: * Set batch size to default size of ring (2048) * Split batches > 2048 into multiples of 2048 or less and process all packets in the same manner that is done for other drivers eg. ixgbe: http://code.dpdk.org/dpdk/v21.02/source/drivers/net/ixgbe/ixgbe_rxtx.c#L318 * Update commit log with reasoning behing batching changes * Update release notes with note on busy polling support * Fix return type for sycall_needed function when the wakeup flag is not present * Apprpriate log leveling * Set default_*xportconf burst sizes to the default busy budget size (64) * Detect support for busy polling via setsockopt instead of using the presence of the flag RFC->v1: * Fixed behaviour of busy_budget=0 * Ensure we bail out any of the new setsockopts fail [1] https://lwn.net/Articles/837010/ Ciara Loftus (3): net/af_xdp: allow bigger batch sizes net/af_xdp: Use recvfrom() instead of poll() net/af_xdp: preferred busy polling doc/guides/nics/af_xdp.rst | 38 ++++- doc/guides/rel_notes/release_21_05.rst | 4 + drivers/net/af_xdp/compat.h | 14 ++ drivers/net/af_xdp/rte_eth_af_xdp.c | 190 ++++++++++++++++++++++--- 4 files changed, 222 insertions(+), 24 deletions(-)