[PATCH v8 12/12] docs: add io_queue flag to isolcpus
From: Daniel Wagner <wagi@kernel.org>
Date: 2025-09-05 15:00:25
Also in:
linux-block, linux-nvme, linux-scsi, lkml
Subsystem:
documentation, the rest · Maintainers:
Jonathan Corbet, Linus Torvalds
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@atomlin.com> Reviewed-by: Hannes Reinecke <hare@suse.de> Signed-off-by: Daniel Wagner <wagi@kernel.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