From patchwork Wed Jul 31 04:38:20 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stephen Hemminger X-Patchwork-Id: 142772 X-Patchwork-Delegate: thomas@monjalon.net Return-Path: 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 45FF1456F9; Wed, 31 Jul 2024 06:43:23 +0200 (CEST) Received: from mails.dpdk.org (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id B7D0D4066C; Wed, 31 Jul 2024 06:43:22 +0200 (CEST) Received: from mail-pl1-f179.google.com (mail-pl1-f179.google.com [209.85.214.179]) by mails.dpdk.org (Postfix) with ESMTP id 30F2C40668 for ; Wed, 31 Jul 2024 06:38:58 +0200 (CEST) Received: by mail-pl1-f179.google.com with SMTP id d9443c01a7336-1fc6ee64512so36823545ad.0 for ; Tue, 30 Jul 2024 21:38:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=networkplumber-org.20230601.gappssmtp.com; s=20230601; t=1722400737; x=1723005537; darn=dpdk.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=I4lo+V5GmN/NemrH3x1aVwcJ0TC1eS0P2sURG1yzpWA=; b=JIGmDcgngQpBh9heqoxXzfx4aMYyuZ5zgZmng9zBotwQPPpy9YO3WyP7ij0VguXGas CEgt5ELlAtTBEBzM0QmwT4e0c1JiWxggIzknbYyAOELb6RT/NGd8K6JGUJaPpjFJ7ATN oF9FtxEvhFG0+//QzqpgLH6MMi+Eu5T8DFrSC5hQsNGmQN7SbouMQrQv6xWGdzGSVKZp GwH2lcxRJNnd46IFN//2vEF7z+7Gt9l3VI8u2VDKw7Mayg3W+b9gtrLpTC64qIiSQRMh M/P0GoDjMC3oUR71zORmgY0coSC6O/rPuPQdGOxssGRSOwPTjmKmWRUvP9MoZgYsjX3j pLBQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1722400737; x=1723005537; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=I4lo+V5GmN/NemrH3x1aVwcJ0TC1eS0P2sURG1yzpWA=; b=eiYCqd6hdLUKJI5O1/RRIfELymfAg5IcndgyOK6MgSEHGj3Yp34tO6OzSug3PWYPH0 eo9ZPBPX4+luOuw1V0mnMXAYdkCrzNfb1oBV9R9oJK4zAcr4IsOVNSh7GNasVNi3JN4J 7DPvf5lVIS9I6LbliSrvDPHyR/XpYa57uycTStilEb+MGppqBvbbdu3FcEZr6Qmai6sI 47MsjrF/w852tkW/NKjgia9N+vQCFB2k5dtTS0NywUFN0fVoByyheRZX4o6MkeDxqx6e j6Ds4JgbeS44D4ZYLm/tunEVVCJbYKCIgpk+LXm2OhMccic4OP9tCSpKuOuDDsnXW/Gj nt2Q== X-Gm-Message-State: AOJu0YzcyP1S3S9dD6f/bCdAD4nMR9MvE9GPr0y10OPTAA0UxM3M0lZD xaa93YPQyatigMOcshyAOK1XrgLZ42n/TrvD1v7n8IO0xr8cYlE8rnYopm4b2NDUOYGq1Q4Nn4F T X-Google-Smtp-Source: AGHT+IENcO0A2Lkfwsau2rr1T866OvaicWyIvbvVXERQjR9CZ9up64VNlMZ6ZWJdEFPF7ss+wmAO8A== X-Received: by 2002:a17:903:234a:b0:1fd:8c25:415d with SMTP id d9443c01a7336-1ff04851ec0mr125951485ad.36.1722400737008; Tue, 30 Jul 2024 21:38:57 -0700 (PDT) Received: from hermes.local (204-195-96-226.wavecable.com. [204.195.96.226]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1fed7c86afasm110911165ad.42.2024.07.30.21.38.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 30 Jul 2024 21:38:56 -0700 (PDT) From: Stephen Hemminger To: dev@dpdk.org Cc: Stephen Hemminger Subject: [PATCH v2 1/2] doc: add note about CPU 0 Date: Tue, 30 Jul 2024 21:38:20 -0700 Message-ID: <20240731043846.78174-1-stephen@networkplumber.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240718184326.21375-1-stephen@networkplumber.org> References: <20240718184326.21375-1-stephen@networkplumber.org> MIME-Version: 1.0 X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org On Linux (and probably BSD), CPU 0 can not be fully isolated because it receives timer interrupts and is used for other kernel related functions. The DPDK documentation should be updated to tell users to avoid polling on that CPU. Signed-off-by: Stephen Hemminger --- doc/guides/linux_gsg/enable_func.rst | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/doc/guides/linux_gsg/enable_func.rst b/doc/guides/linux_gsg/enable_func.rst index 5511640cb8..9f4391456a 100644 --- a/doc/guides/linux_gsg/enable_func.rst +++ b/doc/guides/linux_gsg/enable_func.rst @@ -131,6 +131,11 @@ from running on those cores, it is possible to use the Linux kernel parameters ``isolcpus``, ``nohz_full``, ``irqaffinity`` to isolate them from the general Linux scheduler tasks. +.. note:: + + It is not recommended to use CPU core 0 for DPDK polling applications + because it can not be completely isolated from other system and kernel activity. + For example, if a given CPU has 0-7 cores and DPDK applications are to run on logical cores 2, 4 and 6, the following should be added to the kernel parameter list: