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Wed, 1 Apr 2026 22:24:02 +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, steve@abita.co, sean@ashe.io, chjohnst@gmail.com, neelx@suse.com, mproche@gmail.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux.dev, linux-nvme@lists.infradead.org, linux-scsi@vger.kernel.org, megaraidlinux.pdl@broadcom.com, mpi3mr-linuxdrv.pdl@broadcom.com, MPT-FusionLinux.pdl@broadcom.com Subject: [PATCH v10 13/13] docs: add io_queue flag to isolcpus Date: Wed, 1 Apr 2026 18:23:12 -0400 Message-ID: <20260401222312.772334-14-atomlin@atomlin.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260401222312.772334-1-atomlin@atomlin.com> References: <20260401222312.772334-1-atomlin@atomlin.com> Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: BN1PR13CA0002.namprd13.prod.outlook.com (2603:10b6:408:e2::7) To CWLP123MB3523.GBRP123.PROD.OUTLOOK.COM (2603:10a6:400:70::10) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CWLP123MB3523:EE_|CWLP123MB2964:EE_ X-MS-Office365-Filtering-Correlation-Id: 6fd0a896-4240-4e0b-6ded-08de903d6062 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|7416014|1800799024|366016|56012099003|18002099003|22082099003; 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charset="utf-8" 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. Reviewed-by: Aaron Tomlin Reviewed-by: Hannes Reinecke Signed-off-by: Daniel Wagner Signed-off-by: Aaron Tomlin --- .../admin-guide/kernel-parameters.txt | 22 ++++++++++++++++++- 1 file changed, 21 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentatio= n/admin-guide/kernel-parameters.txt index 03a550630644..9ed7c3ecd158 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2816,7 +2816,6 @@ Kernel parameters "number of CPUs in system - 1". =20 managed_irq - Isolate from being targeted by managed interrupts which have an interrupt mask containing isolated CPUs. The affinity of managed interrupts is @@ -2839,6 +2838,27 @@ Kernel parameters housekeeping CPUs has no influence on those queues. =20 + io_queue + Isolate from I/O queue work caused by multiqueue + device drivers. Restrict the placement of + queues to housekeeping CPUs only, ensuring that + all I/O work is processed by a housekeeping CPU. + + The io_queue configuration takes precedence + over managed_irq. When io_queue is used, + managed_irq placement constrains have no + effect. + + Note: Offlining housekeeping CPUS which serve + isolated CPUs will be rejected. Isolated CPUs + need to be offlined before offlining the + housekeeping CPUs. + + Note: When an isolated CPU issues an I/O request, + it is forwarded to a housekeeping CPU. This will + trigger a software interrupt on the completion + path. + The format of is described above. =20 iucv=3D [HW,NET] --=20 2.51.0