On Wed, Apr 01, 2026 at 06:23:12PM -0400, Aaron Tomlin wrote: > From: Daniel Wagner <[email protected]> > > 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 <[email protected]> > Reviewed-by: Hannes Reinecke <[email protected]> > Signed-off-by: Daniel Wagner <[email protected]> > Signed-off-by: Aaron Tomlin <[email protected]> > --- > .../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
