From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124]) by inbox.dpdk.org (Postfix) with ESMTP id C9D6946B82; Tue, 15 Jul 2025 23:57:30 +0200 (CEST) Received: from mails.dpdk.org (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id 3264B4060F; Tue, 15 Jul 2025 23:57:24 +0200 (CEST) Received: from mail-pl1-f171.google.com (mail-pl1-f171.google.com [209.85.214.171]) by mails.dpdk.org (Postfix) with ESMTP id 4AD454013F for ; Tue, 15 Jul 2025 23:57:22 +0200 (CEST) Received: by mail-pl1-f171.google.com with SMTP id d9443c01a7336-235f9e87f78so54272355ad.2 for ; Tue, 15 Jul 2025 14:57:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=networkplumber-org.20230601.gappssmtp.com; s=20230601; t=1752616641; x=1753221441; 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=OeVkM7mUK3SQbH4YlvR+5Z0uv8xJpwT+OGUGVol5poU=; b=Gt1oSyMO9GpPnZx1TzyZw1xL16T7fIEf88+FioQTx+cDIzr7lVM9+6NcFoKdSBLeyO A9pk/UQJ3/z2oMkk45tDo/708edfhgMfv6eCYqFY1VrQEtiVcAYRkgRn8cjOKxFPQ8mY 0yEwNJ68dV/GFot7A+BpY1dA2osc2uCDQMHAhoZ9xOINfuQ/vQER6nynAlEBWJ0iAW/C jQIG1AZKr0gWX000VkvXRWpVRYzBd+sNkKqbIBQBJMT9ZlKWLm7NmviO2adylvVgaUf3 iHYy1xh8XdOq1H3XPjEVu6PC1611lmBzcSXvnplVy+s2UqjBxHtMEjYf2qzT5EmawZ0m vo0Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1752616641; x=1753221441; 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=OeVkM7mUK3SQbH4YlvR+5Z0uv8xJpwT+OGUGVol5poU=; b=egni9guZbl3tYlcLwWe7Z6qMrZWI8ivBwpFykv0pLJOvQ7UxmM64lt2BoWYbdbW+9d yFSyGR5ueulQoL83LwnqrCbqA/OS/nNadH49QrPABOXx+QKapDL3aA8CxoHU/ACP3HeY 5oLfxXngd5261hSi3AjIXsdWCnKGkiMf51Z938d4Eutjm2isagiCjrTt5rDowle3ioFM k6eKQzpbsnFp99/63unyrQ18DK9j6FoltHoLZL9NxKvN/kqxuoJvuuCcrRVoc1VNkXDz sLTE0yruLFI3tpq/+iU2AyAlzwJCmbnRm9lLM/VXV2ie0AZVpUXACnJNpJX0FH1E8bm3 4dWg== X-Gm-Message-State: AOJu0YyIsnH2ZbNkmn8a8VM31mKfHUpHEQpqGnEp+0sgLLP8i84Sh4GD HuJHP2l7sVcRCmlpnw5M9YkV48sUmVqJvRzEhlP37tkNFtR+m1wO3PKvR3cU5+v76Ktsmil06+v ymw07 X-Gm-Gg: ASbGncs5diEIH7cG/LJxn1cvZPAatntSz3X7BqvyY1h/pGsjjsP+Rh9H/mHFAUt/5uo US6DeihmePRS5GhndKWYGKfd8liMUwLEB5b1dyZWy9Ig7zBC/kys+lRdUehspX8IhQxgSvX3gLq qje/lBW9iw8TfvhLQ0evqUYGvruZxemsrUUrC4PEnm8OYJ2aQRX5A7nDCXQnJH2m6G7SQo+XaGU tzJ4xNl6o0QaDhb06wayz7xr0i8rntBV8Hgb6trev2xUAfhycNYQfaCovkpDE4OgBH5fRc7qK7B 4qnO4FeNX9J1rcTNlAtZShkTd7nEKgkWJq7VBNaMF5KWhtbA58AVrI2HMcig4YJ3hIqZ1vTKwKH c3F1UjaudYpyezZ0hOLS9h+zz65aXk1Yzn4JZ6iA1TRlQ91fKOzKTqQw+86oGOxw177/wSG+7 X-Google-Smtp-Source: AGHT+IEDYMME0zYCmCXjIq3E/8rtScFWvKHUyP+EwuxFsMHlP0Ttu11R0OuzWNvN6Ut5TV7ofJzryQ== X-Received: by 2002:a17:902:ef08:b0:23d:d9ae:3b56 with SMTP id d9443c01a7336-23e256b7467mr5394925ad.22.1752616641397; Tue, 15 Jul 2025 14:57:21 -0700 (PDT) Received: from hermes.lan (204-195-96-226.wavecable.com. [204.195.96.226]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-23de43228a6sm111538185ad.91.2025.07.15.14.57.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 15 Jul 2025 14:57:20 -0700 (PDT) From: Stephen Hemminger To: dev@dpdk.org Cc: Stephen Hemminger Subject: [PATCH v3 1/2] doc: add note about CPU 0 Date: Tue, 15 Jul 2025 14:56:28 -0700 Message-ID: <20250715215718.7388-2-stephen@networkplumber.org> X-Mailer: git-send-email 2.47.2 In-Reply-To: <20250715215718.7388-1-stephen@networkplumber.org> References: <20240718184326.21375-1-stephen@networkplumber.org> <20250715215718.7388-1-stephen@networkplumber.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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..a551ddebec 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 truly 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: -- 2.47.2