linux-kernel - [PATCH v8 12/12] docs: add io

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20250905-isolcpus-io-queues-v8-12-885984c5daca@kernel.org>
Date: Fri, 05 Sep 2025 16:59:58 +0200
From: Daniel Wagner <wagi@...nel.org>
To: Jens Axboe <axboe@...nel.dk>, Keith Busch <kbusch@...nel.org>, 
 Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me>, 
 "Michael S. Tsirkin" <mst@...hat.com>
Cc: Aaron Tomlin <atomlin@...mlin.com>, 
 "Martin K. Petersen" <martin.petersen@...cle.com>, 
 Thomas Gleixner <tglx@...utronix.de>, 
 Costa Shulyupin <costa.shul@...hat.com>, Juri Lelli <juri.lelli@...hat.com>, 
 Valentin Schneider <vschneid@...hat.com>, Waiman Long <llong@...hat.com>, 
 Ming Lei <ming.lei@...hat.com>, Frederic Weisbecker <frederic@...nel.org>, 
 Mel Gorman <mgorman@...e.de>, Hannes Reinecke <hare@...e.de>, 
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, 
 Aaron Tomlin <atomlin@...mlin.com>, linux-kernel@...r.kernel.org, 
 linux-block@...r.kernel.org, linux-nvme@...ts.infradead.org, 
 megaraidlinux.pdl@...adcom.com, linux-scsi@...r.kernel.org, 
 storagedev@...rochip.com, virtualization@...ts.linux.dev, 
 GR-QLogic-Storage-Upstream@...vell.com, Daniel Wagner <wagi@...nel.org>
Subject: [PATCH v8 12/12] docs: add io_queue flag to isolcpus

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 <atomlin@...mlin.com>
Reviewed-by: Hannes Reinecke <hare@...e.de>
Signed-off-by: Daniel Wagner <wagi@...nel.org>
---
 Documentation/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 747a55abf4946bb9efe320f0f62fdcd1560b0a71..4161d4277a7086f2a3726617826c50888eefb260 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2653,7 +2653,6 @@
 			  "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
@@ -2676,6 +2675,27 @@
 			  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.
+
+			  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 <cpu-list> is described above.

 	iucv=		[HW,NET]

-- 
2.51.0