From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from LO2P265CU024.outbound.protection.outlook.com (mail-uksouthazon11021081.outbound.protection.outlook.com [52.101.95.81]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 69BC33A3E74; Wed, 20 May 2026 21:51:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=52.101.95.81 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779313867; cv=fail; b=JA7nuN6x8uGFvTCYvH58RatgKKW23TCtD+PLWmJTqVemRGyg4uWH2IZQi1E39+KAYX5RdDyb1gUZ+SiKgkRyzKphaTX39GJkgHdvm4K/4oZ7ntYwQnZSbvFViJIoLQPEtBA0BPLUW0j/uYb6cucpdGvXjxyTLLcujXLCg/jFXX4= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779313867; c=relaxed/simple; bh=DkYl5gSyzPssM6U7YdR72AEn0X78rHvBW5MNLL/9k2I=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: Content-Type:MIME-Version; b=X9tlphzZeC3WqtGrN61c4twClcfWPGEv1GTg51uYV1v9KyVUeYcBRyCads/bcB2laYP1NRMi6xqIIxvqsh7F1+7cykGdHYW7qYTM57WH37lzI8RtSWjKoxaqZiYZ65mMK4zz+iMviD5y0568D4ikhU3KYnFgyYLOj8KOcBNSpCc= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=atomlin.com; spf=pass smtp.mailfrom=atomlin.com; arc=fail smtp.client-ip=52.101.95.81 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=atomlin.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=atomlin.com ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=TuvlKpgnshsI6D9iSWyd+WGJMCAsjGT56PrgHr64X1Wml9a/CNpAOtvdjjrKfmtlxavrCGfy9IchsFQAQvSJfcUuAy/zcflpqV8qLuZJprXTk9S1UIrwj14fGE3XapZ3AxN0TuLWIFLgrCGUpY73i/dgh3GyzbPmyLSQ9aCeibWXtz3EZ8WGy6FKOjH5sDkFFP/Itnq8zuqjUxTXwVA5ItdRhk8XpLZPVToXVyJTCq4zJXB1l4mxcTxbb5VdMWcCDFFJp2iPzfh09fqSuDemUGbuxZHsFsWz50hg9WEU0KqHizMDnCEpqVR8kdkXoM7otMtd/FAY0EeYCYnsiErDdA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=EbqE/oS98kSBFc5DReMX920shdwvRa0zRECtM01NNo0=; b=SvBAHZ1zxdJG7Wfh8QEZrqSK6Myj2kdzuDAkQ7/LHtnP3fy83b14tzuIaiCUjtjwWbsSvUwsbfveG2hVh6yNqMOBHo8bEpkTswjf876IUbCv1GzaJwkGmRdTPrBYVr/fpgYLySiiY7/F7ZkC8mI33SsDxHm7Lpk54RDoHhWvgHG/VGMVIeWrCKxnkAOTvS2JpXYfCewlFsHoNilHZ4xIMcFEac6pPFtwIg225s1X3+Ekt8IsQkKS3Psy1du2FE0CCY/tgICXYTA1bZ9hww7g6mWy2M2rFEqSLBHJVV9rbXDuch1ZNtDJTwUdeQMdoWWU5xzXG0bsvAtrzu3kKf3S1A== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=atomlin.com; dmarc=pass action=none header.from=atomlin.com; dkim=pass header.d=atomlin.com; arc=none Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=atomlin.com; Received: from CWLP123MB3523.GBRP123.PROD.OUTLOOK.COM (2603:10a6:400:70::10) by LO6P123MB7351.GBRP123.PROD.OUTLOOK.COM (2603:10a6:600:37e::11) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.48.14; Wed, 20 May 2026 21:51:02 +0000 Received: from CWLP123MB3523.GBRP123.PROD.OUTLOOK.COM ([fe80::de8e:2e4f:6c6:f3bf]) by CWLP123MB3523.GBRP123.PROD.OUTLOOK.COM ([fe80::de8e:2e4f:6c6:f3bf%2]) with mapi id 15.20.9846.025; Wed, 20 May 2026 21:51:02 +0000 From: Aaron Tomlin To: axboe@kernel.dk, kbusch@kernel.org, hch@lst.de, sagi@grimberg.me, mst@redhat.com Cc: atomlin@atomlin.com, aacraid@microsemi.com, James.Bottomley@HansenPartnership.com, martin.petersen@oracle.com, liyihang9@h-partners.com, kashyap.desai@broadcom.com, sumit.saxena@broadcom.com, shivasharan.srikanteshwara@broadcom.com, chandrakanth.patil@broadcom.com, sathya.prakash@broadcom.com, sreekanth.reddy@broadcom.com, suganath-prabu.subramani@broadcom.com, ranjan.kumar@broadcom.com, jinpu.wang@cloud.ionos.com, tglx@kernel.org, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, akpm@linux-foundation.org, maz@kernel.org, ruanjinjie@huawei.com, bigeasy@linutronix.de, yphbchou0911@gmail.com, wagi@kernel.org, frederic@kernel.org, longman@redhat.com, chenridong@huawei.com, hare@suse.de, kch@nvidia.com, ming.lei@redhat.com, tom.leiming@gmail.com, steve@abita.co, sean@ashe.io, chjohnst@gmail.com, neelx@suse.com, mproche@gmail.com, nick.lange@gmail.com, marco.crivellari@suse.com, rishil1999@outlook.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v14 8/8] docs: add io_queue flag to isolcpus Date: Wed, 20 May 2026 17:50:30 -0400 Message-ID: <20260520215030.496803-9-atomlin@atomlin.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260520215030.496803-1-atomlin@atomlin.com> References: <20260520215030.496803-1-atomlin@atomlin.com> Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: MN0PR05CA0022.namprd05.prod.outlook.com (2603:10b6:208:52c::22) To CWLP123MB3523.GBRP123.PROD.OUTLOOK.COM (2603:10a6:400:70::10) Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CWLP123MB3523:EE_|LO6P123MB7351:EE_ X-MS-Office365-Filtering-Correlation-Id: b812b7c0-813e-46e4-fb70-08deb6b9e2c3 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|376014|1800799024|366016|3023799007|22082099003|56012099003|18002099003; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:CWLP123MB3523.GBRP123.PROD.OUTLOOK.COM;PTR:;CAT:NONE;SFS:(13230040)(7416014)(376014)(1800799024)(366016)(3023799007)(22082099003)(56012099003)(18002099003);DIR:OUT;SFP:1102; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?gkcyv4tzrVDBiSvNBfxVKjiiGR2ujHMSNYmekEpIyk9l3LHMEqOLtjHkKjGx?= =?us-ascii?Q?+KXh1+sYhP74G/dHwR79QK7/n75s4MRfcweeIETsQ5UMncyedl48Z6FlyeIt?= =?us-ascii?Q?a/rBBgCJgZDwTF+vtlP9U4eppQ7CSI9JDUXAtPrQ2BX9I6D11m7DetruupIY?= =?us-ascii?Q?X3fpsbPJ3+GbPkS9QlpYN5q0gMMpx2187b3rxQmG79rekvAnkssQiNX4oDTg?= =?us-ascii?Q?JKXCH4Muy2Pa2BaBRaP99O/8p9qgd1tTWa4M82RN2V1avIie3k9IRMlZs3hg?= =?us-ascii?Q?qLM5rUkwJTzMpLfvMDuLHjMGi8pj+WC1ejgsCJIarrPOO4MMPUg64jiEx/iX?= =?us-ascii?Q?USIoNvZlGf7gSf6+c9ks5UMm41LS2248Dt2givWlP8O09lh4qKQvy8NYCGJE?= =?us-ascii?Q?XTpA/tQj0YTWk3r0MzGOS0pW1OC6dNyhfFNI4d00dNkhwldlmhwiGfszAeoT?= =?us-ascii?Q?aWE2PT9AAM4A+nfTVbNAGdTjjSj/Jgi0SDAgYtbrwLejhawfHmbm9BC88ALh?= =?us-ascii?Q?HM+gMZ/y6npfU8LCaTNp1PQUS3Q5miPR0txQaXyu4A/nPkZhhKzMJYmPDI/h?= =?us-ascii?Q?XGOlhcqGhQJqFag48n1YILpoKE7RotdlvN8A5znaHIOhTjzqUMJg0o98xpaM?= =?us-ascii?Q?cs2vD1xA5dNQ6zcwzQq8QP/N6SqfJHObZ7nApbC4kWBB0zhK9dHV6LskDKPD?= =?us-ascii?Q?DXaimE7Ksd2VYnfduPoaqqxl6e7pFIPNFjwjqg4dPD4X5KpRABbbV9SkhkbI?= =?us-ascii?Q?VYUSzNrknnNd5Ur8SGRhBYaIdl62pEGFkNzV2SIz6txAEmjjgW/AxIlhoCk3?= =?us-ascii?Q?WUXUEiv7s97rYrpVnf9yzFp+ItL5gJr38cBz6pVu094EqxK0jfiRqB/WSz7n?= =?us-ascii?Q?u+AR2NEx9Qap5mVnMTt77G7hhEFhJfqEC9PU8VXPlmgOkss4gbXqpgGtdnoP?= =?us-ascii?Q?I01kVO4ZaIDd8n64YrOP9+B7DV/prxG2Dr45+VBsFFLA3crSXpw73oTUovCw?= =?us-ascii?Q?nAfxek/gXok35+jIXeD9PCz/453p7ls0nKYsooyg3dx7e6qxHDZCQ+4LD8wt?= =?us-ascii?Q?suBm4/JCHnbmHlDqxLK6mxMlUQIHanvOU60njwQ5dScRD/S4u+GwK8gw3F9c?= =?us-ascii?Q?1RgMNHdqYkJilG6FJ8f8lc9PYlLAzV7YOtfOTJcxHQ1pGv67FhXN/8SiHOBO?= =?us-ascii?Q?czijOofHtPgaCn31koQJwp80ZNXUfhtctJx8WGGfLhkGtaX9rSriilJV8woP?= =?us-ascii?Q?hsdSQA5aiDtkC1m5SNiEg26QZAUg0DnZwWCznakYqDAAZNb9krnO0Y+qxOlk?= =?us-ascii?Q?LFHqp25lVwDP/Qi4oFQ4GtFMJ73+HlF01DeaYWBGY6fWO0koAetL15g6M1zO?= =?us-ascii?Q?PEUnBzp0mh4DoNIeg1OmxPg9BaEShgyaCjxWwPGYtkinmk0ftKtFhlqH3a1d?= =?us-ascii?Q?C0aH+F3gXo9KIqEBLTj6lrq+WHK8WRBnm2J5ZcuH2SchGzzaHBZpq3AvVcZu?= =?us-ascii?Q?f4dheizhuLwzt2em/MgB8BLtucpN5h2kW9XMXv0z2JfbUX+kaV6YHUxvlSoo?= =?us-ascii?Q?O9PRkCqaezNOYF3TUIHOfu+uNaH9RyPaSjNs4bOJNBJOxH0jFrvyTh2D+ELL?= =?us-ascii?Q?+XtIBE+j3EIoU9kbjDA6ti93pyNXASWJC9HYMw3LxGfcoeLgvV2oOmC3Heol?= =?us-ascii?Q?ORLWocUH+VqvrfRIISP63bipcTUQzmPUmsxvywPGseDmE6eLEbbFb8cWgjKz?= =?us-ascii?Q?l5HMajEU1g=3D=3D?= X-OriginatorOrg: atomlin.com X-MS-Exchange-CrossTenant-Network-Message-Id: b812b7c0-813e-46e4-fb70-08deb6b9e2c3 X-MS-Exchange-CrossTenant-AuthSource: CWLP123MB3523.GBRP123.PROD.OUTLOOK.COM X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 20 May 2026 21:51:02.5810 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: e6a32402-7d7b-4830-9a2b-76945bbbcb57 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: GZt/bdAO851e14ZFaGIy0VP8U+oZ8m7Jc8ddRA9JfuI3mQwESya7Lu//IBmE+8lsXIR2JaeslESIIvLwDUTqgg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: LO6P123MB7351 From: Daniel Wagner The io_queue flag informs multiqueue device drivers where to place hardware queues. Document this new flag in the isolcpus command-line argument description. Signed-off-by: Daniel Wagner Reviewed-by: Hannes Reinecke [atomlin: - Refined io_queue kernel parameter documentation - Removed an inaccurate claim in the documentation stating that io_queue takes precedence over managed_irq] Signed-off-by: Aaron Tomlin --- .../admin-guide/kernel-parameters.txt | 26 ++++++++++++++++++- 1 file changed, 25 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 4d0f545fb3ec..fb828bb60b9e 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2792,7 +2792,6 @@ Kernel parameters "number of CPUs in system - 1". managed_irq - Isolate from being targeted by managed interrupts which have an interrupt mask containing isolated CPUs. The affinity of managed interrupts is @@ -2815,6 +2814,31 @@ Kernel parameters housekeeping CPUs has no influence on those queues. + io_queue + Applicable to managed IRQs only. Restrict + multiqueue hardware queue allocation to online + housekeeping CPUs. This guarantees that all + managed hardware completion interrupts are routed + exclusively to housekeeping cores, shielding + isolated CPUs from I/O interruptions even if they + initiated the request. + + Note: Using io_queue restricts the number of + allocated hardware queues to match the number of + housekeeping CPUs. This prevents MSI-X vector + exhaustion and forces isolated CPUs to share + submission queues. + + Note: Offlining housekeeping CPUs which serve + isolated CPUs will fail. The isolated CPUs must + be offlined before offlining the housekeeping + CPUs. + + Note: When I/O is submitted by an application on + an isolated CPU, the hardware completion + interrupt is handled entirely by a housekeeping + CPU. + The format of is described above. iucv= [HW,NET] -- 2.51.0