Re: [PATCH v6 6/9] isolation: introduce io_queue isolcpus type

[Daniel Wagner]

On Fri, Apr 25, 2025 at 08:26:22AM +0200, Hannes Reinecke wrote:
> On 4/24/25 20:19, Daniel Wagner wrote:
> > Multiqueue drivers spreading IO queues on all CPUs for optimal
> > performance. The drivers are not aware of the CPU isolated requirement
> > and will spread all queues ignoring the isolcpus configuration.
> > 
> > Introduce a new isolcpus mask which allows the user to define on which
> > CPUs IO queues should be placed. This is similar to the managed_irq but
> > for drivers which do not use the managed IRQ infrastructure.
> > 
> > Signed-off-by: Daniel Wagner <wagi@xxxxxxxxxx>
> > ---
> >   include/linux/sched/isolation.h | 1 +
> >   kernel/sched/isolation.c        | 7 +++++++
> >   2 files changed, 8 insertions(+)
> > 
> Reviewed-by: Hannes Reinecke <hare@xxxxxxx>

Just realized I forgot to also add some document on this new argument:

			io_queue
			  Isolate from IO queue work caused by multiqueue
			  device drivers. Restrict the placement of
			  queues to housekeeping CPUs only, ensuring that
			  all IO work is processed by a housekeeping CPU.

			  Note: When an isolated CPU issues an IO, it is
			  forwarded to a housekeeping CPU. This will
			  trigger a software interrupt on the completion
			  path.

			  Note: It is not possible to offline housekeeping
			  CPUs that serve isolated CPUs.