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Thu, 02 Apr 2026 22:30:59 -0400 X-MC-Unique: rCXx2cJTP-Klv46VrVi2tw-1 X-Mimecast-MFC-AGG-ID: rCXx2cJTP-Klv46VrVi2tw_1775183455 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 752D518005B0; Fri, 3 Apr 2026 02:30:53 +0000 (UTC) Received: from fedora (unknown [10.72.116.83]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 3908A1801A52; Fri, 3 Apr 2026 02:30:30 +0000 (UTC) Date: Fri, 3 Apr 2026 10:30:26 +0800 From: Ming Lei To: Aaron Tomlin Cc: axboe@kernel.dk, kbusch@kernel.org, hch@lst.de, sagi@grimberg.me, mst@redhat.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, 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: Re: [PATCH v10 13/13] docs: add io_queue flag to isolcpus Message-ID: References: <20260401222312.772334-1-atomlin@atomlin.com> <20260401222312.772334-14-atomlin@atomlin.com> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260401222312.772334-14-atomlin@atomlin.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 On Wed, Apr 01, 2026 at 06:23:12PM -0400, Aaron Tomlin wrote: > 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/Documentation/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". > > 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. > > + 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. All these can be supported by `managed_irq` already, please document the thing which `io_queue` solves, and `managed_irq` can't cover, so user can know how to choose between the two command lines. `Restrict the placement of queues to housekeeping CPUs only` looks totally stale, please see patch 10, in which isolated CPUs are spread too. > + > + 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. `io_queue` doesn't touch io completion code path, which is more implementation details, so not sure if the above Note is needed. Thanks, Ming